Health Education Systems Inc (HESI) A2 Exam Quiz: Newtons Laws Of Motion
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Newtons Laws Of MotionQuestion 1 of 20

A patient in a wheelchair is accidentally bumped, causing it to start moving. Which of the following physical properties is a direct measure of the patient and wheelchair's combined resistance to this change in their state of rest?

Weight
Velocity
Mass
Acceleration
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Health Education Systems Inc (HESI) A2 Exam Quiz

Health Education Systems Inc (HESI) A2 Exam Quiz: Newtons Laws Of Motion

Practice Newtons Laws Of Motion in Health Education Systems Inc (HESI) A2 Exam with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Newtons Laws Of Motion, giving you a quick way to practice the rules, question types, and explanations that matter most for Health Education Systems Inc (HESI) A2 Exam.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A patient in a wheelchair is accidentally bumped, causing it to start moving. Which of the following physical properties is a direct measure of the patient and wheelchair's combined resistance to this change in their state of rest?

  1. Weight
  2. Velocity
  3. Mass (correct answer)
  4. Acceleration
Explanation: When you encounter physics problems on the HESI involving motion and resistance to change, you're dealing with fundamental concepts of inertia and mass. The key principle here is Newton's First Law: objects at rest tend to stay at rest unless acted upon by an external force. Mass (C) is the correct answer because it directly measures how much matter an object contains and determines its resistance to changes in motion. When the wheelchair is bumped, the combined mass of the patient and wheelchair determines how much they resist starting to move. The greater the mass, the more force needed to change their state of rest. Mass is an intrinsic property that doesn't change regardless of location or motion. Weight (A) is tempting because it's related to mass, but weight is actually the force of gravity acting on mass (Weight=mass×gravityWeight = mass \times gravity). Weight can vary depending on gravitational conditions, making it an indirect rather than direct measure of resistance to motion changes. Velocity (B) describes how fast something moves in a particular direction. Since the wheelchair starts at rest, velocity is initially zero and doesn't measure resistance to change. Acceleration (D) measures the rate of change in velocity. Like velocity, this describes motion after the change occurs, not the resistance to that change. For HESI physics questions, remember that mass is always the fundamental property determining inertia—an object's tendency to resist changes in motion. When you see questions about "resistance to change in motion," think mass first.

Question 2

A caregiver helps a patient walk by pulling forward on the patient's arm with a constant force. The patient moves forward at a constant velocity. According to Newton's laws, which force must be equal in magnitude to the caregiver's pulling force?

  1. The force of the patient pulling backward on the caregiver's arm.
  2. The sum of all resistive forces, such as friction and air resistance, acting on the patient. (correct answer)
  3. The patient's weight.
  4. The net force on the patient.
Explanation: When you encounter physics problems involving constant velocity motion, immediately think about Newton's First Law and the concept of equilibrium. If an object moves at constant velocity, the net force acting on it must be zero, meaning all forces are balanced. Since the patient moves forward at constant velocity while being pulled, the caregiver's forward pulling force must be exactly balanced by opposing forces. These opposing forces include friction between the patient's feet and the ground, air resistance, and any other resistive forces that naturally oppose motion. The sum of all these resistive forces equals the pulling force in magnitude but acts in the opposite direction, creating equilibrium. This makes B correct. Let's examine why the other options are incorrect. Choice A describes Newton's Third Law (action-reaction pairs), but this force acts on the caregiver, not the patient, so it doesn't affect the patient's motion. Choice C, the patient's weight, acts vertically downward and is balanced by the normal force from the ground - this vertical force pair doesn't relate to the horizontal motion described. Choice D, the net force on the patient, must be zero since the patient moves at constant velocity, so it cannot equal the pulling force unless that force is also zero. For HESI physics questions, remember that constant velocity always means balanced forces. When analyzing forces, separate horizontal from vertical components and identify what opposes the applied force to maintain equilibrium.

Question 3

A certain net force F causes a medication cart of mass m to have an acceleration a. If both the net force applied to the cart and the mass of the cart are doubled, what is the new acceleration of the cart?

  1. a (correct answer)
  2. 2a
  3. a/2
  4. 4a
Explanation: When you encounter physics problems involving Newton's second law, always start with the fundamental relationship: F=maF = ma, where force equals mass times acceleration. Let's work through this systematically. Initially, you have force F, mass m, and acceleration a, so F=maF = ma. Now the problem doubles both the force and mass, giving you a new force of 2F and a new mass of 2m. Using Newton's second law again: 2F=(2m)×anew2F = (2m) \times a_{new} To find the new acceleration, solve for anewa_{new}: anew=2F2m=Fma_{new} = \frac{2F}{2m} = \frac{F}{m} Since the original relationship was a=Fma = \frac{F}{m}, the new acceleration equals the original acceleration a. Looking at the wrong answers: Choice B (2a) assumes you only considered the doubled force while ignoring the doubled mass - a common error when students focus on just one changing variable. Choice C (a/2) represents the mistake of thinking the doubled mass reduces acceleration by half without accounting for the doubled force. Choice D (4a) occurs when students incorrectly multiply both effects together (2 × 2 = 4) rather than recognizing they cancel each other out. The correct answer is A) a because doubling both force and mass simultaneously results in no net change to acceleration. Study tip: For Newton's second law problems, remember that acceleration depends on the ratio of force to mass. When both numerator and denominator change by the same factor, the ratio - and therefore acceleration - remains constant.

Question 4

Which of the following scenarios describes a pair of forces that is NOT a valid action-reaction pair as defined by Newton's third law?

  1. A patient's foot pushes down on a floor scale, and the floor scale pushes up on the patient's foot.
  2. The Earth's gravity pulls a falling apple downward, and the apple's gravity pulls the Earth upward.
  3. The downward force of gravity on a resting patient is balanced by the upward normal force from the bed. (correct answer)
  4. A syringe plunger pushes fluid forward, and the fluid pushes backward on the plunger.
Explanation: When you encounter Newton's third law questions, focus on identifying true action-reaction pairs versus situations where forces happen to be balanced. Newton's third law states that for every action, there is an equal and opposite reaction - but these forces must act on different objects and be of the same fundamental type. Option C describes balanced forces, not an action-reaction pair. The downward gravitational force acts on the patient, while the upward normal force from the bed also acts on the patient. Since both forces act on the same object (the patient), they cannot be an action-reaction pair according to Newton's third law. These forces are simply in equilibrium, keeping the patient at rest. Option A represents a valid action-reaction pair: the foot pushes down on the scale (action), and the scale pushes up on the foot (reaction) - different objects experiencing opposite forces. Option B is also correct: Earth pulls the apple downward (action), and the apple pulls Earth upward (reaction) with equal gravitational force. Option D shows another valid pair: the plunger pushes fluid forward (action), and the fluid pushes back on the plunger (reaction). The key distinction is that action-reaction pairs involve forces acting on different objects, while balanced forces act on the same object. On physics questions, watch for this common misconception where equilibrium situations are confused with Newton's third law pairs. Remember: action-reaction forces never act on the same object.

Question 5

A fast-moving hospital gurney is suddenly stopped when it collides with a wall. A box that was resting on the gurney's lower shelf flies forward. Which principle best explains why the box continues to move forward after the gurney stops?

  1. Newton's Third Law, as the gurney exerts a forward reaction force on the box.
  2. The force of the impact with the wall is transferred through the gurney to the box.
  3. Newton's First Law (Inertia), as the box tended to remain in its state of motion. (correct answer)
  4. Newton's Second Law, as the sudden stop created a large forward acceleration for the box.
Explanation: When you encounter physics problems involving objects in motion that suddenly stop or change direction, you're typically dealing with Newton's laws of motion. The key is identifying which law governs the specific situation described. In this scenario, the box continues moving forward because of Newton's First Law, also known as the law of inertia. This law states that an object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless acted upon by an external force. When the gurney was moving, the box was also moving at the same speed. When the gurney suddenly stopped due to hitting the wall, no immediate force acted directly on the box to stop it, so it continued moving forward at its original velocity. Let's examine why the other options are incorrect. Option A incorrectly applies Newton's Third Law, which deals with action-reaction force pairs between objects in contact. The gurney hitting the wall doesn't create a forward reaction force on the box. Option B suggests force transfer through the gurney, but the collision force actually stops the gurney rather than propelling the box forward. Option D misapplies Newton's Second Law by claiming the stop created forward acceleration for the box, when in reality, the box maintains its original motion while the gurney decelerates. Remember this pattern: when you see objects continuing to move after their "carrier" stops suddenly, think inertia first. These questions test whether you can distinguish between an object maintaining its existing motion versus being acted upon by a new force.

Question 6

A hospital gurney with a total mass of 150 kg is rolling down a hall. An orderly applies a constant net force of 75 N in the direction opposite to its motion to slow it down. What is the magnitude of the gurney's deceleration?

  1. 0.5 m/s² (correct answer)
  2. 2.0 m/s²
  3. 75 m/s²
  4. 150 m/s²
Explanation: When you encounter physics problems involving forces and motion, you're working with Newton's Second Law: F=maF = ma. This fundamental equation tells you that net force equals mass times acceleration, and you can rearrange it to solve for any of the three variables. In this problem, you have a 150 kg gurney slowing down due to a 75 N force applied opposite to its motion. Since you need deceleration (which is just acceleration in the opposite direction), rearrange the equation to solve for acceleration: a=Fma = \frac{F}{m}. Substituting the values: a=75 N150 kg=0.5 m/s2a = \frac{75 \text{ N}}{150 \text{ kg}} = 0.5 \text{ m/s}^2 This gives you answer choice A) 0.5 m/s². Let's examine why the other options are incorrect. Choice B) 2.0 m/s² results from incorrectly dividing mass by force (15075\frac{150}{75}) instead of force by mass. Choice C) 75 m/s² occurs when students forget to divide by mass entirely, just using the force value. Choice D) 150 m/s² happens when students use only the mass value, completely ignoring the force. Remember that acceleration always has units of m/s², and the magnitude should make physical sense. A deceleration of 0.5 m/s² is reasonable for slowing down a hospital gurney, while 75 or 150 m/s² would be extremely violent decelerations that could damage equipment or injure patients. Always check that your calculated acceleration is physically reasonable for the given scenario.

Question 7

A physical therapist applies the same net force to two different objects at rest. Object A has a mass of 10 kg, and Object B has a mass of 20 kg. According to Newton's Second Law, how does the acceleration of Object A compare to that of Object B?

  1. The acceleration of Object A is half the acceleration of Object B.
  2. The acceleration of Object A is double the acceleration of Object B. (correct answer)
  3. The accelerations of both objects are equal because the applied net force is the same.
  4. The acceleration of Object B is four times the acceleration of Object A.
Explanation: When you encounter physics problems involving forces and motion, Newton's Second Law is your foundation: Force equals mass times acceleration, or F=maF = ma. Rearranging this equation gives us a=Fma = \frac{F}{m}, which shows that acceleration is inversely proportional to mass when force remains constant. Since the same net force is applied to both objects, you can set up the relationship: aA=FmAa_A = \frac{F}{m_A} and aB=FmBa_B = \frac{F}{m_B}. With Object A having mass 10 kg and Object B having mass 20 kg, Object A's acceleration becomes aA=F10a_A = \frac{F}{10} while Object B's acceleration is aB=F20a_B = \frac{F}{20}. Comparing these: aAaB=F/10F/20=2010=2\frac{a_A}{a_B} = \frac{F/10}{F/20} = \frac{20}{10} = 2. Therefore, Object A accelerates twice as fast as Object B. Option A incorrectly reverses this relationship, suggesting the lighter object accelerates less. This contradicts Newton's Second Law. Option C falls into the trap of thinking equal forces produce equal accelerations, ignoring the crucial role of mass. Option D creates an arbitrary four-fold difference that has no basis in the given masses or physics principles. Remember this key pattern: when the same force acts on objects of different masses, the lighter object always accelerates more. This inverse relationship between mass and acceleration appears frequently on physics problems, so practice identifying when forces are constant and masses vary.

Question 8

When a syringe plunger is pushed, the plunger exerts a force on the fluid, and the fluid exerts an equal and opposite force on the plunger. Why do these forces not cancel each other out, allowing the fluid to be expelled?

  1. The force exerted on the fluid is slightly greater than the force exerted on the plunger.
  2. The forces act on different objects and cannot cancel each other out. (correct answer)
  3. The inertia of the plunger is much less than the inertia of the fluid.
  4. The pressure created inside the syringe overcomes the reaction force from the fluid.
Explanation: This question tests your understanding of Newton's third law of motion and how forces interact between different objects in a system. When you push a syringe plunger, Newton's third law does apply - the plunger exerts a force on the fluid, and the fluid exerts an equal and opposite force back on the plunger. However, these forces don't prevent the fluid from moving because they act on different objects. The force you apply pushes on the fluid (causing it to accelerate toward the needle), while the reaction force pushes back on the plunger (which you counteract with your hand). Since these forces act on separate objects - the fluid and the plunger - they cannot cancel each other out to prevent motion. Choice A incorrectly suggests the forces are unequal, which would violate Newton's third law. The action and reaction forces are always equal in magnitude. Choice C mentions inertia, but this doesn't explain why the forces don't cancel - inertia relates to an object's resistance to changing motion, not force cancellation. Choice D focuses on pressure overcoming reaction force, but this misses the key point that forces on different objects simply cannot cancel each other. For physics questions on the HESI, remember that Newton's third law always produces equal and opposite forces, but these force pairs act on different objects. Forces can only cancel when they act on the same object. This distinction frequently appears in questions about mechanical systems and fluid dynamics.

Question 9

A wheelchair is at rest at the top of a hospital ramp. What condition is necessary for the wheelchair to begin accelerating down the ramp?

  1. The normal force from the ramp must be greater than the gravitational force on the wheelchair.
  2. The force of static friction must be exactly equal to the component of gravity pulling the wheelchair down the ramp.
  3. The patient must push backward, as an object at rest naturally stays at rest without an external push.
  4. The component of gravity pulling the wheelchair down the ramp must be greater than the maximum force of static friction. (correct answer)
Explanation: When you encounter physics problems involving objects on inclined surfaces, you're dealing with force equilibrium and the conditions that cause motion to begin or stop. A wheelchair at rest on a ramp has several forces acting on it: gravity (pulling straight down), the normal force (perpendicular to the ramp surface), and static friction (parallel to the ramp surface, opposing potential motion). For the wheelchair to remain stationary, the force of static friction must balance the component of gravitational force pulling it down the ramp. The moment this balance is broken—when gravity's pull exceeds friction's maximum resistance—acceleration begins. Option D correctly identifies this threshold: motion starts when the gravitational component down the ramp overcomes the maximum static friction force. This is the fundamental principle of inclined plane physics. Option A is incorrect because the normal force and gravitational force act in different directions and don't directly compete—the normal force is perpendicular to the ramp while gravity acts vertically downward. Option B describes the equilibrium condition where the wheelchair remains at rest, not the condition for acceleration to begin. Option C misapplies Newton's first law. While objects at rest do tend to stay at rest, the wheelchair doesn't need a backward push from the patient—gravity provides the force once friction is overcome. Remember this pattern for HESI physics questions: when analyzing motion on inclined surfaces, always break forces into components and identify what happens when static friction reaches its maximum value. This is typically where motion begins.

Question 10

A nurse pushes an IV pole at a constant velocity across a level hospital floor. Which statement best describes the forces acting on the IV pole in the horizontal direction?

  1. The force exerted by the nurse is greater than the force of friction, which is why the pole is moving forward.
  2. The force exerted by the nurse is equal in magnitude to the force of friction. (correct answer)
  3. The inertia of the IV pole is the primary force that the nurse must overcome to maintain the constant motion.
  4. There are no horizontal forces acting on the pole because its velocity is constant and it is not accelerating.
Explanation: When you encounter physics problems involving constant velocity motion, remember that constant velocity means zero acceleration, and by Newton's First Law, this requires balanced forces. Since the IV pole moves at constant velocity, its acceleration is zero. Newton's First Law tells us that when acceleration is zero, the net force must also be zero. This means all horizontal forces acting on the pole must be perfectly balanced. The nurse applies a forward force to push the pole, while friction from the floor creates an opposing backward force. For the pole to maintain constant velocity, these forces must be equal in magnitude, making choice B correct. Let's examine why the other options are incorrect. Choice A suggests the nurse's force exceeds friction, which would create a net forward force and cause the pole to accelerate, contradicting the constant velocity condition. Choice C incorrectly identifies inertia as a force—inertia is actually an object's resistance to changes in motion, not a force itself. Choice D makes the error of assuming no forces exist just because velocity is constant. In reality, multiple forces are present; they're simply balanced. The key insight is distinguishing between "no net force" and "no forces at all." Objects moving at constant velocity experience balanced forces, not an absence of forces. HESI tip: Physics questions often test whether you understand that constant velocity requires balanced forces, not the absence of forces. Always consider what forces are present and whether they're balanced when analyzing motion scenarios.

Question 11

A medical textbook rests motionless on a bedside table. According to Newton's third law of motion, what is the reaction force to the gravitational force of the Earth pulling the book downward?

  1. The upward normal force exerted by the table on the book.
  2. The gravitational force of the book pulling the Earth upward. (correct answer)
  3. The frictional force between the book and the surface of the table.
  4. There is no reaction force because the book is not accelerating.
Explanation: When you encounter questions about Newton's third law, remember that it states every action has an equal and opposite reaction. The key is identifying the correct force pair - forces that act on different objects and are equal in magnitude but opposite in direction. The gravitational force in question is Earth pulling the book downward. According to Newton's third law, the reaction force must be the book pulling Earth upward with equal magnitude. This is choice B - the gravitational force of the book pulling the Earth upward. Even though Earth is vastly more massive than the book, the gravitational attraction is mutual and equal in strength. Choice A represents a common misconception. The upward normal force from the table is indeed equal and opposite to the book's weight, but this describes equilibrium, not Newton's third law. The normal force and weight act on the same object (the book), while Newton's third law pairs involve forces on different objects. Choice C is incorrect because friction between the book and table surface isn't related to the gravitational force pair. Friction would only be relevant if the book were sliding or attempting to slide. Choice D misunderstands Newton's third law entirely. Reaction forces always exist regardless of whether objects are accelerating. The law applies to all force interactions, not just those producing motion. Remember: Newton's third law force pairs always act on different objects. When Earth pulls on the book, the book simultaneously pulls on Earth. Look for this "different objects" pattern to identify correct force pairs on physics questions.

Question 12

A large ambulance collides head-on with a small, stationary passenger car. During the moment of impact, which statement is true according to Newton's third law?

  1. The ambulance exerts a greater force on the car than the car exerts on the ambulance due to its larger mass.
  2. The car exerts a greater force on the ambulance because it experiences a much larger acceleration.
  3. The ambulance exerts a force on the car that is equal in magnitude to the force the car exerts on the ambulance. (correct answer)
  4. The forces are only equal if the ambulance was also stationary before the collision.
Explanation: When you encounter collision problems, remember that Newton's third law states that for every action, there is an equal and opposite reaction. This means that forces always come in pairs - when object A exerts a force on object B, object B simultaneously exerts an equal magnitude force back on object A, regardless of their masses or motion states. In this collision, the ambulance pushes on the car with a certain force, and simultaneously, the car pushes back on the ambulance with exactly the same magnitude of force in the opposite direction. This is true at every instant during the collision, making answer C correct. Let's examine why the other options are wrong: Answer A incorrectly suggests that the larger mass of the ambulance means it exerts a greater force. Mass affects the acceleration each vehicle experiences (F=maF = ma), but Newton's third law guarantees equal force magnitudes regardless of mass differences. Answer B confuses force with acceleration. While the smaller car will indeed experience much greater acceleration due to its lower mass, the forces between the vehicles remain equal in magnitude. Remember: a=F/ma = F/m, so smaller mass means larger acceleration for the same force. Answer D wrongly implies that Newton's third law only applies when both objects are stationary. The law applies universally - whether objects are moving, stationary, accelerating, or at constant velocity. For physics questions on the HESI, always distinguish between force pairs (which are always equal by Newton's third law) and the different accelerations or velocities that result from those forces acting on objects with different masses.

Question 13

An object is observed to be moving in a straight line at a constant speed of 10 m/s. Which of the following statements about the object MUST be true?

  1. There is a constant net force acting on the object in the direction of its motion.
  2. The net force acting on the object is zero. (correct answer)
  3. There are no forces of any kind acting on the object.
  4. The object's inertia is greater than any force of friction acting upon it.
Explanation: When you encounter physics problems involving motion, always start by identifying what type of motion is occurring and then apply Newton's laws accordingly. This question tests your understanding of Newton's First Law of Motion and the relationship between forces and motion. An object moving in a straight line at constant velocity (constant speed in a constant direction) has zero acceleration. According to Newton's First Law, an object at rest or in uniform motion will remain in that state unless acted upon by an unbalanced net force. Since there's no change in velocity, the acceleration is zero, which means the net force must also be zero by Newton's Second Law (Fnet=maF_{net} = ma). Answer choice A is incorrect because a constant net force in the direction of motion would cause the object to accelerate, increasing its speed continuously. This contradicts the given constant speed condition. Answer choice C represents a common misconception. Forces can still act on the object (like friction, air resistance, or applied forces), but they must be balanced so the net force equals zero. For example, if you push a box across a floor at constant speed, your applied force exactly balances the friction force. Answer choice D confuses concepts by comparing inertia (an object's resistance to changes in motion) with force. Inertia isn't "greater than" friction; rather, the forces acting on the object are simply balanced. Remember this key principle: constant velocity always means zero net force, regardless of how many individual forces might be acting on the object. Focus on the word "net" when analyzing force problems.

Question 14

A nurse pushes a medication cart from rest, causing it to accelerate. If the cart is accelerating to the north, what can be definitively concluded about the net force acting on it?

  1. The velocity of the cart is directed to the north.
  2. The force applied by the nurse is greater than the cart's weight.
  3. The net force on the cart is directed to the north. (correct answer)
  4. The only force on the cart is directed to the north.
Explanation: When you encounter physics problems involving motion and forces, always connect acceleration directly to net force through Newton's Second Law: Fnet=maF_{net} = ma. This fundamental relationship tells you that acceleration and net force always point in the same direction. Since the cart accelerates northward, Newton's Second Law definitively tells you the net force must also be directed northward. This makes option C correct - it's a direct application of the most fundamental law of motion. Let's examine why the other options contain flawed reasoning: Option A confuses acceleration with velocity. While the cart accelerates north, its velocity could initially be in any direction (or zero). Acceleration tells you how velocity is changing, not the velocity's current direction. The cart could even be moving south while accelerating north (slowing down). Option B incorrectly compares horizontal and vertical forces. The nurse's horizontal push doesn't need to exceed the cart's vertical weight for northward acceleration - these forces act in perpendicular directions. The cart can accelerate horizontally regardless of how the horizontal push compares to its weight. Option D assumes only one force acts on the cart, but multiple forces likely exist: the nurse's push, friction, possibly air resistance, and the cart's weight. What matters isn't having just one force, but having a net force (the vector sum of all forces) pointing north. Remember this key principle: acceleration direction always equals net force direction, regardless of individual forces or current velocity. On physics questions, distinguish between individual forces and net force - they're often quite different.

Question 15

A large, heavy supply cabinet and a small, light stool are both at rest in a storage room. Assuming friction is negligible, which statement correctly compares the two objects based on Newton's laws?

  1. The cabinet requires a greater net force to achieve the same acceleration as the stool. (correct answer)
  2. The stool has more inertia than the cabinet because it is easier to move.
  3. The inertia of both objects is zero because they are currently at rest.
  4. Both objects require the same net force to be set into motion from rest.
Explanation: When you encounter questions about forces and motion, you're dealing with Newton's laws, particularly the relationship between force, mass, and acceleration expressed in Newton's second law: F=maF = ma. The key insight here involves understanding inertia and how mass affects the force needed to produce acceleration. Inertia is an object's resistance to changes in motion, and it's directly proportional to mass. Since the cabinet is described as "large and heavy" while the stool is "small and light," the cabinet has significantly more mass. Using Newton's second law, if both objects need to achieve the same acceleration, the cabinet will require a proportionally larger force because F=maF = ma. For example, if the cabinet has 10 times the mass of the stool, it needs 10 times the force to achieve the same acceleration. This makes choice A correct. Choice B incorrectly confuses ease of movement with inertia. The stool is easier to move precisely because it has less inertia (less mass), not more. Choice C reflects a fundamental misconception—inertia depends on mass, not motion. Both objects have inertia whether moving or at rest; being at rest doesn't eliminate their resistance to acceleration. Choice D ignores the mass difference entirely. While any non-zero force will eventually move either object (since friction is negligible), different forces are needed to produce the same acceleration. Remember this pattern: when comparing objects of different masses, the more massive object always requires greater force to achieve the same acceleration. Mass and required force are directly proportional when acceleration is constant.

Question 16

When a rocket engine expels hot gas backward, the rocket accelerates forward into space. This phenomenon is best explained by:

  1. Newton's First Law alone, as the rocket must overcome its inertia to begin moving.
  2. Newton's Second Law alone, as the force generated by the engine causes the rocket to accelerate.
  3. Newton's Third Law alone, as the action of expelling gas has an equal and opposite reaction.
  4. A combination of Newton's Second and Third Laws. (correct answer)
Explanation: When you encounter questions about forces and motion, especially involving rockets or projectiles, you need to consider how Newton's laws work together to explain the complete physical phenomenon. A rocket's movement involves multiple physics principles simultaneously. As the engine burns fuel and expels hot gas backward at high velocity, Newton's Third Law creates the primary mechanism: for every action (gas expelled backward), there's an equal and opposite reaction (forward thrust on the rocket). However, this thrust force then acts on the rocket's mass according to Newton's Second Law (F=maF = ma), causing the rocket to accelerate forward. The greater the thrust force or the lighter the rocket becomes (as fuel burns), the greater the acceleration. Option A is incomplete because while Newton's First Law explains that the rocket needs force to overcome inertia, it doesn't explain how that force is generated or how acceleration occurs. Option B captures part of the physics—the relationship between force and acceleration—but ignores the crucial mechanism of how the thrust force is created through gas expulsion. Option C identifies the key action-reaction principle but misses how that reaction force translates into actual motion of the rocket. Option D correctly recognizes that rocket propulsion requires both the action-reaction pair (Third Law) to generate thrust and the force-acceleration relationship (Second Law) to produce motion. Remember: Complex motion problems on the HESI often test whether you can identify multiple physics principles working together rather than looking for a single law in isolation.

Question 17

According to Newton's second law of motion, which of the following statements is NOT correct?

  1. An object's acceleration is directly proportional to its mass. (correct answer)
  2. The net force on an object moving at a constant velocity is zero.
  3. If the net force on an object is doubled, its acceleration is also doubled.
  4. An object's acceleration occurs in the same direction as the net force.
Explanation: Newton's second law of motion is one of the fundamental principles in physics, expressed as F=maF = ma (force equals mass times acceleration). This law describes the relationship between the forces acting on an object and its resulting motion. Let's examine what this law actually tells us. When you apply a net force to an object, the acceleration it experiences depends on both the force applied and the object's mass. Specifically, acceleration is directly proportional to the net force and inversely proportional to the mass. Option A incorrectly states that acceleration is directly proportional to mass. This is backwards—acceleration is actually inversely proportional to mass. If you double an object's mass while keeping force constant, the acceleration decreases by half. Think of pushing a shopping cart versus pushing a car with the same force. Option B is correct because if an object moves at constant velocity, its acceleration is zero, which means the net force must also be zero (since F=maF = ma and a=0a = 0). Option C is correct because if you double the net force while mass remains constant, acceleration doubles proportionally (a=F/ma = F/m). Option D is correct because Newton's second law shows that acceleration occurs in the same direction as the net force applied. When studying Newton's laws for the HESI, remember that the second law is all about the relationship F=maF = ma. Focus on understanding that force and acceleration are directly related, while mass and acceleration are inversely related. This inverse relationship with mass is the most commonly tested concept.

Question 18

If a person is pushing a heavy, wheeled oxygen tank and it is not moving, what is the relationship between the pushing force and the force of static friction?

  1. The pushing force is greater than the force of static friction.
  2. The force of static friction is greater than the pushing force.
  3. The pushing force is equal in magnitude to the force of static friction. (correct answer)
  4. There is no static friction because the oxygen tank is not moving.
Explanation: When you encounter physics problems involving objects that aren't moving despite applied forces, you're dealing with static equilibrium and Newton's First Law. The key insight is that if an object remains at rest, all forces acting on it must be perfectly balanced. In this scenario, someone is pushing on a heavy oxygen tank that won't budge. Since the tank remains stationary, the net force on it must be zero. This means the force being applied by the person must be exactly counteracted by an equal and opposite force - in this case, static friction between the tank's wheels and the floor. Static friction is a responsive force that automatically adjusts to match the applied force, up to its maximum limit. As long as the pushing force doesn't exceed the maximum static friction available, the friction force will equal the pushing force, keeping the object motionless. Option A is incorrect because if the pushing force were greater than static friction, the tank would accelerate forward according to Newton's Second Law. Option B is wrong because if friction were greater than the pushing force, there would be a net force backward, which doesn't happen with static friction - it only responds to match the applied force. Option D reflects a common misconception; static friction exists precisely because there's a force trying to cause motion, even when no motion occurs. For HESI physics questions, remember that "no motion" always means "balanced forces." When objects don't move despite applied forces, look for equal and opposite force pairs.

Question 19

A patient stands on a scale in an elevator that is accelerating upward. How will the scale's reading of the patient's apparent weight compare to their actual weight?

  1. It will be equal to the patient's actual weight.
  2. It will be greater than the patient's actual weight. (correct answer)
  3. It will be less than the patient's actual weight.
  4. It will be zero.
Explanation: When you encounter physics problems involving apparent weight and acceleration, think about the forces acting on an object and how they combine to create the sensation of weight. In this scenario, two forces act on the patient: gravity pulling downward with force mgmg (their true weight), and the elevator floor pushing upward. When the elevator accelerates upward, Newton's second law tells us that the net upward force must exceed the gravitational force to produce this acceleration. This means the normal force from the scale must be greater than the patient's actual weight. From the patient's perspective, they feel "heavier" because the elevator floor is pushing up on them with extra force to accelerate their body upward along with the elevator. The scale reads this increased normal force, which is the apparent weight. Choice A incorrectly assumes the scale reading remains unchanged, ignoring the effect of acceleration. Choice C represents the opposite scenario—what would happen if the elevator were accelerating downward, where you'd feel lighter. Choice D would only occur in free fall or if the elevator cable snapped, creating a weightless sensation. The correct answer is B: the scale reading will be greater than the patient's actual weight. Remember this pattern: upward acceleration always increases apparent weight, while downward acceleration decreases it. On the HESI, physics questions often test whether you can identify how forces combine in accelerating reference frames—always consider both gravity and the additional forces created by acceleration.

Question 20

An astronaut has a mass of 80 kg on Earth. When this astronaut is on the Moon, where the acceleration due to gravity is approximately 1/6th that of Earth, what are the astronaut's mass and weight?

  1. Mass is approximately 13.3 kg, and weight is the same as on Earth.
  2. Mass is 80 kg, and weight is the same as on Earth.
  3. Mass is 80 kg, and weight is approximately 1/6th of their weight on Earth. (correct answer)
  4. Mass is approximately 13.3 kg, and weight is approximately 1/6th of their weight on Earth.
Explanation: When you encounter questions about objects in different gravitational environments, remember that mass and weight are fundamentally different properties. Mass measures the amount of matter in an object and remains constant regardless of location, while weight is the gravitational force acting on that mass and varies with gravitational strength. The astronaut's mass of 80 kg represents the actual amount of matter in their body. This quantity doesn't change whether they're on Earth, the Moon, or floating in space - it's an intrinsic property of the astronaut themselves. Weight, however, equals mass times gravitational acceleration (W=mgW = mg). On Earth, the astronaut weighs 80 kg×9.8 m/s2=784 N80 \text{ kg} \times 9.8 \text{ m/s}^2 = 784 \text{ N}. On the Moon, where gravity is 1/6th of Earth's, their weight becomes 80 kg×(9.8/6) m/s2=131 N80 \text{ kg} \times (9.8/6) \text{ m/s}^2 = 131 \text{ N}, which is indeed 1/6th their Earth weight. Answer A incorrectly suggests mass changes to 13.3 kg while weight stays the same - this reverses the actual relationship. Answer B correctly identifies that mass remains 80 kg but wrongly claims weight doesn't change between planets. Answer D makes both errors: incorrectly changing the mass to 13.3 kg while correctly noting the weight reduction. For HESI physics questions, always distinguish between mass (intrinsic, unchanging) and weight (gravitational force, location-dependent). When gravitational acceleration changes, only weight is affected - mass remains constant.