AP Physics 1 Quiz: Newtons First Law

What this quiz covers

This quiz focuses on Newtons First Law, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 1.

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.

Question 1

1. Gravity is greater than air resistance because the ball is moving downward.
2. Air resistance is greater than gravity because the ball has inertia.
3. Gravity equals air resistance because the net force is zero. (correct answer)
4. Air resistance is zero because the ball is not accelerating.

Explanation: This question assesses understanding of Newton's First Law of Motion, explaining terminal velocity as constant velocity with zero net force. The ball falls downward at constant velocity, meaning its acceleration is zero. According to Newton's First Law, zero acceleration implies the net force is zero. The downward gravitational force equals the upward air resistance force. Choice A is incorrect because it embodies the misconception that motion requires the driving force (gravity) to be greater, but at constant velocity, forces balance. A transferable strategy is to recognize terminal velocity as a balance point and compare magnitudes of opposing forces like drag and weight.

Question 2

1. The spring force upward equals the weight downward. (correct answer)
2. Only gravity acts because the object is not moving.
3. The net force is downward because gravity is always unbalanced.
4. The spring force upward must be greater than the weight to prevent motion.

Explanation: This question assesses understanding of Newton's First Law of Motion, which states that an object at rest stays at rest with zero net force. The object hangs motionless, so the net vertical force is zero. The downward weight is balanced by the upward spring force, keeping it in equilibrium. This balance prevents any acceleration or movement. Choice D is incorrect because it suggests the spring force must exceed the weight to prevent motion, misunderstanding that equal forces suffice for rest under Newton's First Law. A transferable approach is to identify equilibrium conditions and set opposing forces equal when there's no change in velocity.

Question 3

1. A net force acts north to maintain the puck’s northward motion.
2. The net force is zero because the puck’s velocity is constant. (correct answer)
3. A net force acts south to oppose the puck’s motion.
4. The puck has a net force north equal to its momentum divided by time.

Explanation: This question assesses understanding of Newton's First Law of Motion, which states that an object in uniform motion remains in that state without a net external force. The puck is sliding at a constant velocity of 5.0 m/s north, indicating zero net force acting on it. With negligible friction and air resistance, no unbalanced forces alter its motion, so it continues straight at constant speed. This demonstrates inertia, where the puck resists changes to its velocity. Choice A is wrong as it suggests a net force is needed to maintain motion, a common misconception that force is required for constant velocity rather than for acceleration. For similar scenarios, remember to equate constant velocity with zero net force and draw free-body diagrams to confirm balanced forces.

Question 4

1. The net force points in the direction of motion because it is moving.
2. The net force is zero because the acceleration is zero. (correct answer)
3. The net force equals the weight because gravity is the strongest force.
4. The net force equals the friction force because friction sets the motion.

Explanation: This question assesses understanding of Newton's First Law of Motion, which links constant velocity to zero net force. The crate moves at constant speed, indicating no net force acts on it. The horizontal push balances the kinetic friction force, resulting in zero acceleration. All forces sum to zero, allowing steady motion. Choice A is incorrect as it claims net force aligns with motion direction, a misconception that force is required to maintain velocity instead of to change it. For these questions, use the strategy of confirming zero acceleration from constant speed and ensuring net force calculations reflect that balance.

Question 5

1. It is north because the car is moving north.
2. It is south because resistive forces oppose motion.
3. It is zero because the driving force equals the total resistive force. (correct answer)
4. It is zero only if the engine is off.

Explanation: This question assesses understanding of Newton's First Law of Motion, which explains that constant velocity occurs when no net force acts. The car travels north at constant speed, so its horizontal velocity is unchanging, indicating zero horizontal acceleration. Newton's First Law requires that the net horizontal force be zero for this to happen. The northward driving force from the engine balances the southward resistive forces like air resistance and friction. Choice A is mistaken because it reflects the misconception that motion requires a net force in the direction of motion, but inertia allows constant velocity without any net force. A transferable strategy is to separate force analysis into horizontal and vertical components and confirm balance when velocity is constant in a given direction.

Question 6

1. Zero, because constant velocity implies zero acceleration. (correct answer)
2. Eastward, because motion requires a force in the direction of motion.
3. Westward, because friction must oppose the motion even if small.
4. Downward, because gravity is unbalanced while the puck is moving.

Explanation: This question assesses understanding of Newton's First Law of Motion, which states that an object in motion continues with constant velocity unless acted upon by a net force. The puck is sliding east at constant velocity, meaning its speed and direction are unchanging, so its acceleration is zero. Newton's First Law indicates that zero acceleration requires the net force to be zero. All forces on the puck—gravity downward and normal force upward—balance vertically, and there are no unbalanced horizontal forces since friction is negligible. Choice B is wrong because it embodies the misconception that motion requires a force in the direction of motion, whereas constant velocity persists without any net force due to inertia. A transferable strategy is to check for constant velocity; if present, ensure the vector sum of forces is zero by considering all directions separately.

Question 7

1. Approximately $0\ \text{N}$. (correct answer)
2. A constant force northward to maintain the motion.
3. A constant force downward equal to $mg$.
4. A constant force upward equal to $mg$.

Explanation: This question tests Newton's First Law applied to horizontal motion with constant velocity. The puck slides north at a constant 5.0 m/s on nearly frictionless ice, meaning its velocity is unchanging. Newton's First Law states that constant velocity requires zero net force—the puck needs no force to maintain its motion. The puck experiences downward gravity and upward normal force, which balance each other vertically, and negligible horizontal forces due to the frictionless surface. The common misconception is that motion in a direction requires force in that direction, but this violates Newton's First Law. Remember that objects in motion stay in motion at constant velocity when net force equals zero—approximately 0 N in this case.

Question 8

1. $0\ \text{N}$ because the sign is not moving.
2. $10\ \text{N}$.
3. $98\ \text{N}$. (correct answer)
4. $196\ \text{N}$.

Explanation: This question tests Newton's First Law for a hanging object in equilibrium. The sign hangs motionless, meaning its velocity is zero and remains zero—a state of equilibrium. Newton's First Law requires that zero velocity (rest) means zero net force, so the vertical forces must balance. The sign experiences downward weight of mg = 10 kg × 9.8 m/s² = 98 N, and the upward tension must equal this for zero net force. The misconception that stationary objects experience zero force confuses zero net force with zero individual forces. To solve hanging object problems, recognize that equilibrium requires the tension to exactly balance the weight, making tension equal to mg.

Question 9

1. The normal force is greater than the rider’s weight.
2. The net force on the rider is upward because the rider is moving upward.
3. The normal force equals the rider’s weight. (correct answer)
4. The normal force is less than the rider’s weight.

Explanation: This question tests Newton's First Law for vertical motion at constant velocity. The elevator and rider move upward at a constant 2.0 m/s, meaning the rider's velocity is unchanging. According to Newton's First Law, constant velocity (even upward) requires zero net force, so all forces on the rider must balance. The rider experiences downward weight (mg) and upward normal force from the scale, and these must be equal for zero net force. The misconception that upward motion requires greater normal force than weight ignores that constant velocity means zero acceleration and thus zero net force. When analyzing elevator problems, focus on whether the velocity is changing—constant velocity always means the normal force equals the weight.

Question 10

1. Tension is greater than kinetic friction because the crate is moving right.
2. Kinetic friction is greater than tension because friction opposes motion.
3. Tension equals kinetic friction in magnitude. (correct answer)
4. There is no friction because the crate’s speed is constant.

Explanation: This question tests Newton's First Law applied to horizontal forces during constant-speed motion. The crate moves right at constant speed, meaning its horizontal velocity is unchanging. Newton's First Law requires that constant velocity means zero net force, so the horizontal forces must balance. The rope provides rightward tension while kinetic friction acts leftward to oppose the motion, and these two horizontal forces must be equal in magnitude for the net horizontal force to be zero. The misconception that motion requires greater force in the direction of motion ignores that constant speed means balanced forces. To analyze constant-speed problems, identify all forces in the direction of motion and perpendicular to it, then apply the condition that forces must balance in each direction.

Question 11

1. The net force is eastward because the cart is moving east.
2. The net force is zero because the cart’s velocity is constant. (correct answer)
3. The net force is upward because the normal force is larger than the weight.
4. The net force is westward because friction acts westward.

Explanation: This question tests Newton's First Law, which states that an object maintains constant velocity when the net force is zero. The cart moves east at a constant 3.0 m/s, meaning its velocity (both speed and direction) is unchanging. According to Newton's First Law, constant velocity requires zero net force—all forces must balance. The eastward motion does not require an eastward force to maintain it; this is the common misconception that motion requires force in the direction of motion. Since the cart experiences gravity downward, normal force upward, and small friction westward, these forces must sum to zero. When analyzing motion problems, always check if velocity is constant—if so, the net force must be zero regardless of the direction of motion.

Question 12

1. The net force is east because thrust acts east.
2. The net force is west because drag opposes the motion.
3. The net force is zero because all forces balance. (correct answer)
4. The net force is upward because buoyancy keeps the boat afloat.

Explanation: This question tests Newton's First Law for multi-directional forces at constant velocity. The boat moves east at constant velocity, meaning both its speed and direction remain unchanged. Newton's First Law states that constant velocity requires zero net force—all forces in all directions must balance. Horizontally, the eastward engine thrust must equal the westward water drag, while vertically, the upward buoyancy must equal the downward weight. The misconception that motion direction determines net force direction ignores that constant velocity always means balanced forces. When analyzing objects with forces in multiple directions, check that forces balance separately in each direction (horizontal and vertical) for true equilibrium.

Question 13

1. The driving force is greater than resistive forces because the car is moving forward.
2. The resistive forces are greater than the driving force because friction always wins.
3. The driving force equals the total resistive force in magnitude. (correct answer)
4. No horizontal forces act once the car reaches constant speed.

Explanation: This question assesses understanding of Newton's First Law of Motion, which explains that an object at constant velocity experiences zero net force. The car travels at constant velocity, so horizontal forces must balance. The forward driving force equals the total backward resistive forces in magnitude, resulting in no acceleration. This maintains the steady speed despite ongoing forces. Choice A is wrong as it assumes the driving force must exceed resistance to keep the car moving, a misconception that force is needed for motion itself rather than for changing motion. In similar problems, apply the principle that constant velocity implies zero net force and check for equality among opposing forces.

Question 14

1. The net horizontal force is $1.5\ \text{N}$ west because it is moving east.
2. The net horizontal force is zero because the forces to the east and west balance. (correct answer)
3. There is no friction because the cart is moving at constant speed.
4. A constant eastward net force is required to keep the cart moving.

Explanation: This question assesses understanding of Newton's First Law of Motion, which states that an object in motion continues in uniform motion unless acted upon by a net external force. Since the cart is moving at a constant velocity of 3.0 m/s east, the net horizontal force on it must be zero. This means all horizontal forces, including the 1.5 N westward force from the fan and any frictional forces, balance out to produce no acceleration. Constant velocity implies that the forces to the east and west are equal in magnitude, resulting in equilibrium. Choice D is incorrect because it reflects the misconception that a constant net force is required to maintain motion, whereas Newton's First Law clarifies that no net force is needed for constant velocity. To analyze similar problems, always check if velocity is constant and conclude that net force is zero, then identify balancing forces.

Question 15

1. The net force is east because the car has an eastward velocity.
2. The net force is west because resistive forces always dominate motion.
3. The net force is zero because forward and backward forces balance. (correct answer)
4. The net force is zero only if the engine is turned off.

Explanation: This question tests Newton's first law, which requires zero net force for constant velocity motion. The car moves east at constant speed on a straight road, meaning its velocity is constant and acceleration is zero. According to Newton's first law, this requires the net force to be zero. The engine provides a forward (eastward) force, while air drag and rolling resistance provide backward (westward) forces. For the car to maintain constant velocity, these forward and backward forces must be equal in magnitude, resulting in zero net force. Choice A incorrectly assumes that eastward velocity requires an eastward net force, illustrating the misconception that motion requires force in the direction of motion. When analyzing constant velocity scenarios, always conclude that the net force is zero and all forces balance.

Question 16

1. The net force is downward because the box would fall without the rope.
2. The net force is upward because tension is an active force.
3. The net force is zero because the forces balance. (correct answer)
4. The net force is zero only if the rope has no mass.

Explanation: This question tests your understanding of Newton's first law. The box hangs motionless, which means it remains at rest with zero velocity. According to Newton's first law, an object at rest has zero net force acting on it. The box experiences two forces: the upward tension in the rope and the downward gravitational force (weight = mg). Since the box remains at rest, these forces must be equal in magnitude and opposite in direction, resulting in zero net force. Choice B incorrectly suggests a net upward force because tension is "active," reflecting the misconception that preventing motion (keeping the box from falling) requires net force. When analyzing static equilibrium, always remember that zero velocity means zero net force.

Question 17

1. The net force is north because thrust is the cause of the motion.
2. The net force is south because drag always exceeds thrust at constant speed.
3. The net force is zero because the thrust and drag are equal in magnitude. (correct answer)
4. The net force is zero only if the boat is not moving.

Explanation: This question tests Newton's first law for horizontal motion at constant velocity. The boat travels north at constant velocity, meaning its acceleration is zero and the net force must be zero. Two horizontal forces act: engine thrust north and water drag south. For the boat to maintain constant velocity, these forces must be equal in magnitude and opposite in direction, resulting in zero net force. Choice A incorrectly assumes that northward motion requires a north net force because thrust causes the motion, illustrating the misconception that motion requires force. When analyzing constant velocity situations, focus on the current state of motion (constant velocity) rather than what initially caused the motion—constant velocity always means zero net force.

Question 18

1. $100\ \text{N}$ up the ramp
2. $50\ \text{N}$ up the ramp
3. $0\ \text{N}$ (correct answer)
4. $50\ \text{N}$ down the ramp

Explanation: This question tests your understanding of Newton's first law. The crate moves up the ramp at constant velocity, which means its velocity is not changing. According to Newton's first law, constant velocity requires zero net force. Along the ramp direction, the applied push of 50 N up the ramp is exactly balanced by the combined effect of friction and gravity's component (50 N down the ramp). These forces are equal in magnitude and opposite in direction, so they cancel completely, resulting in a net force of 0 N parallel to the ramp. Choice A incorrectly suggests the net force equals the applied force, reflecting the misconception that motion up a ramp requires net force up the ramp. When analyzing forces on inclines, remember that constant velocity still means zero net force.

Question 19

1. The net force is east because the car is moving east.
2. The net force is zero because the forward and resistive forces balance. (correct answer)
3. The net force is west because resistive forces always dominate.
4. The net force is zero only if the engine is off.

Explanation: This question tests your understanding of Newton's first law. The car travels at constant speed (20 m/s) in a straight line, which means its velocity is not changing. According to Newton's first law, when an object maintains constant velocity, the net force on it must be zero. The forward traction force from the engine must exactly balance the combined resistive forces (air resistance and rolling resistance) acting opposite to the motion. Since these forces balance, the net force is zero. Choice A incorrectly assumes that motion eastward requires a net force eastward, which is a common misconception that motion requires force. To analyze such problems, focus on whether velocity is changing—constant velocity always means zero net force.

Question 20

1. The table’s normal force on the book equals the book’s weight in magnitude. (correct answer)
2. The book has no forces on it because it is not moving.
3. Gravity is balanced by a force of inertia, not by the table.
4. The normal force must be greater than the weight to keep the book from sinking.

Explanation: This question assesses understanding of Newton's First Law of Motion, which explains that an object at rest remains at rest unless acted upon by a net external force. The book is at rest on the table, so the net force on it must be zero. This means the downward gravitational force (weight) is exactly balanced by the upward normal force from the table. Since there is no motion, these vertical forces are equal in magnitude and opposite in direction, maintaining equilibrium. Choice B is incorrect because it embodies the misconception that no forces act on stationary objects, ignoring that balanced forces can keep an object at rest without motion. When approaching such problems, identify all forces acting on the object and verify that they sum to zero for cases of rest or constant velocity.