A block is pressed against a vertical wall by a horizontal push and remains at rest. Static friction is present between block and wall. The push is horizontal.
Which forces act on the block?
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AP Physics 1 Quiz
Practice Forces And Free Body Diagrams in AP Physics 1 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.
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A block is pressed against a vertical wall by a horizontal push and remains at rest. Static friction is present between block and wall. The push is horizontal.
Which forces act on the block?
This quiz focuses on Forces And Free Body Diagrams, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 1.
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.
A block is pressed against a vertical wall by a horizontal push and remains at rest. Static friction is present between block and wall. The push is horizontal.
Which forces act on the block?
Explanation: This question examines free-body diagrams for objects in static equilibrium against vertical surfaces with friction. Choose the block as the system and list external forces from contacts. The forces are weight downward, the applied horizontal push into the wall, normal force from the wall outward, and static friction upward opposing weight to prevent sliding. Equilibrium requires friction to balance weight vertically and normal to balance the push horizontally. Choice B is incorrect because it shows friction downward, which would not counteract weight and allow the block to fall. For such scenarios, ensure frictional forces are directed to oppose potential motion, and verify balance in all directions for rest conditions.
A car rounds a flat (unbanked) curve at constant speed. Static friction between tires and road is present; air resistance is negligible.
Which force provides the car’s horizontal acceleration toward the center of the curve?
Explanation: This question assesses understanding of forces providing centripetal acceleration in circular motion on flat surfaces. Select the car as the system and identify forces causing the inward acceleration. Static friction between tires and road acts toward the center of the curve, providing the necessary horizontal force for turning at constant speed. Other forces like weight and normal are vertical and do not contribute horizontally. Choice D is incorrect because there is no 'force in the direction of motion'; centripetal force is perpendicular to tangential velocity. A key strategy is to recognize that centripetal force comes from real forces like friction, directed inward, and separate it from tangential forces affecting speed.
A block is on a horizontal surface and is pulled by a rope horizontally to the right. Friction is negligible. The block accelerates to the right.
Which free-body diagram description is correct?
Explanation: This question evaluates constructing free-body diagrams for accelerating objects with tension and negligible friction. Choose the block as the system and include forces from its environment. The real forces are weight downward, normal force upward from the surface, and tension to the right from the rope. With negligible friction and acceleration to the right, tension provides the net horizontal force. Choice D is incorrect because it includes a 'force of motion,' which is not a real force but a misconception. Always base free-body diagrams on actual physical interactions, and for acceleration, ensure net force direction matches the acceleration vector per Newton's second law.
A 2.0 kg book rests on a horizontal table. Friction is negligible. The book is pulled to the right by a horizontal string with tension 6.0 N, and it accelerates to the right. Which set of forces acts on the book?
Stem: Which free-body diagram correctly represents the forces on the book?
Explanation: This question assesses the skill of identifying forces and constructing free-body diagrams in AP Physics 1. To create a correct free-body diagram, select the book as the system and identify all external forces acting on it. The real forces include the gravitational force mg downward from Earth, the normal force upward from the table, and the tension force of 6.0 N to the right from the string. No frictional force is present since friction is negligible, and there is no additional force in the direction of motion as acceleration results from the net force, not an extra force. Choice C is incorrect because it includes an extra force in the direction of motion, which is a common misconception but not a real force; motion does not require a separate force beyond the existing unbalanced forces. Always isolate the object and list only contact and field forces acting on it, ensuring no fictitious forces like 'force of acceleration' are included.
A puck moves at constant velocity across level ice. Friction and air resistance are negligible. Which forces act on the puck?
Explanation: This problem tests understanding of forces on an object in uniform motion with no friction. When creating a free-body diagram, we choose the puck as our system and identify only real forces acting on it. The puck experiences two forces: its weight (mg) downward from gravity and the normal force upward from the ice surface. Since the puck moves at constant velocity with no friction or air resistance, there is no net force, and these vertical forces balance each other. Choice A incorrectly includes a "forward force in the direction of motion" - objects in motion don't require forces to maintain constant velocity, only to change velocity. Remember Newton's first law: an object at constant velocity has zero net force.
A box is pulled up a rough incline at constant velocity by a rope parallel to the incline. Kinetic friction is present. Which force acts on the box along the incline?
Explanation: This problem requires identifying forces along an inclined plane with friction. When analyzing forces on an incline, we consider components parallel to the surface and choose the box as our system. Along the incline, the box experiences the parallel component of weight pointing down the incline, the tension from the rope up the incline, and kinetic friction down the incline (opposing the motion up). Since the box moves at constant velocity, these forces along the incline must sum to zero. Choice A incorrectly shows friction up the incline - kinetic friction always opposes the direction of motion, so it must point down since the box moves up. When solving incline problems with friction, always draw kinetic friction opposite to the velocity direction.
A sled moves down a snowy hill that makes a 25∘ angle with the horizontal. Friction is negligible. The sled is accelerating down the slope. Which forces act on the sled?
Stem: Which set of forces correctly describes the sled’s free-body diagram?
Explanation: This question assesses the skill of identifying forces and constructing free-body diagrams in AP Physics 1. Select the sled as the system and account for its interaction with the environment on the inclined surface. The real forces are the gravitational force mg straight downward from Earth and the normal force perpendicular to the slope from the hill. No frictional force acts since friction is negligible, and the acceleration down the slope comes from the component of gravity parallel to the incline, not an additional force. Choice D is incorrect because it includes a separate force down the slope due to motion, which is not a real force; the downhill acceleration is solely due to the unbalanced component of gravity. To build accurate free-body diagrams on inclines, always draw gravity vertically downward and normal force perpendicular to the surface, resolving components as needed for analysis.
A 1.2kg box slides down a rough 25∘ incline and speeds up. Kinetic friction is present.
Which force direction for friction on the box is correct?
Explanation: This question tests your ability to identify forces in a free-body diagram, specifically the direction of kinetic friction. When analyzing forces on the sliding box, we have weight (downward), normal force (perpendicular to the incline surface), and kinetic friction. Kinetic friction always opposes the relative motion between surfaces - since the box slides down the incline, friction acts up the incline. Choice A incorrectly states friction acts down the incline in the direction of motion, but friction never aids motion - it always opposes it. The key strategy is to remember that kinetic friction always acts opposite to the direction of sliding along the surface.
A sled is pulled right by a rope on a frictionless horizontal surface and speeds up. Friction is negligible. Which forces act on the sled?
Explanation: This problem tests identifying forces on an accelerating object on a frictionless surface. When drawing a free-body diagram, we choose the sled as our system and include only forces acting directly on it. The sled experiences three forces: weight (mg) downward from gravity, normal force upward from the surface (perpendicular to the surface), and tension to the right from the rope pulling it. Since friction is negligible and the sled speeds up to the right, the tension provides the net horizontal force causing acceleration. Choice B incorrectly includes a "force of motion" - motion is a result of forces, not a force itself. For any object on a horizontal surface, always include both weight and normal force, even on frictionless surfaces.
A student carries a 5.0N textbook across a room at constant velocity. The book is held level in one hand. Air resistance is negligible.
Which forces act on the book?
Explanation: This question tests your ability to identify forces in a free-body diagram for a carried object. The book experiences weight (downward) and the hand must provide two forces: an upward force to support against gravity and a forward force to maintain the constant velocity motion (overcoming any small resistances). These are both contact forces from the hand. Choice A incorrectly includes a "force of motion" - motion results from forces but is not itself a force. The key strategy is to recognize that a single contact (like the hand) can provide forces in multiple directions as needed to maintain the object's state of motion.
A 2.0kg book is pushed across a horizontal table at constant velocity. Kinetic friction is present. The push is horizontal.
Which set of forces acts on the book?
Explanation: This question tests your ability to identify forces in a free-body diagram. When analyzing forces on the book, we must identify only the real forces acting directly on it: weight (gravitational force downward), normal force (support force from the table upward), kinetic friction (opposing motion, so opposite to the direction of movement), and the applied push (in the direction of motion). Since the book moves at constant velocity, these forces must be balanced. Choice C incorrectly includes a "force of motion" which is not a real force, and incorrectly states there's no normal force - the table must push up on the book to support it against gravity. The key strategy is to identify only real forces that result from interactions with other objects, never include fictitious "forces of motion."
A 2.0kg box is pulled across a horizontal floor at constant velocity by a horizontal rope. Kinetic friction is present. Which forces act on the box?
Select the correct free-body diagram.
Explanation: This problem requires identifying forces in a free-body diagram for a box being pulled at constant velocity. When drawing a free-body diagram, we choose the box as our object and include only forces that directly act on it. The forces are: weight (mg) acting downward due to gravity, normal force acting upward from the floor supporting the box, tension acting horizontally in the direction of the pull (to the right), and kinetic friction acting opposite to the direction of motion (to the left). Choice D incorrectly includes a 'force of motion' to the right, but motion is not a force—it's the result of forces. Since the box moves at constant velocity, the net force is zero, meaning tension and friction are equal and opposite. The key strategy is to identify only real forces from interactions with other objects (Earth, floor, rope) and never include fictitious forces like 'force of motion.'
A 2.0kg book rests on a horizontal table. Friction is negligible. The book is at rest (no acceleration). Which forces act on the book?
Explanation: This problem tests your understanding of forces and free-body diagrams for objects at rest. When analyzing forces on an object, we must identify all real forces acting directly on that object - in this case, the book. The book experiences two forces: its weight (mg) acting downward due to Earth's gravitational pull, and the normal force from the table pushing upward on the book. Since the book is at rest with no acceleration, these forces must be balanced. Choice C incorrectly includes a "force in the direction of motion," but there is no motion and no such force exists - forces cause motion, not the other way around. Remember: for any object resting on a surface, always include weight downward and normal force perpendicular to the surface.
A 0.80kg block is pressed against the ceiling by an upward applied force and remains at rest. Friction is negligible. Which forces act on the block?
Select the correct free-body diagram.
Explanation: This problem requires identifying forces in a free-body diagram for a block pressed against a ceiling at rest. When drawing a free-body diagram, we select the block as our object and include only forces acting directly on it. The forces are: weight (mg) acting downward from gravity, applied force acting upward from the push, and normal force acting downward from the ceiling (the ceiling pushes down on the block). Choice C incorrectly shows the normal force from the ceiling as upward, but the ceiling is above the block and pushes down on it—normal forces always push away from surfaces. Since the block is at rest, forces balance: the upward applied force equals the sum of weight and normal force, both downward. The essential strategy is to recognize that normal forces always push outward from surfaces, and when an object is pressed against a surface, that surface pushes back on the object.
A 0.20kg ball is thrown straight upward and is moving upward but slowing down. Air resistance is negligible. Which forces act on the ball?
Select the correct free-body diagram.
Explanation: This problem requires identifying forces in a free-body diagram for a ball thrown upward while slowing down. When constructing a free-body diagram, we choose the ball as our object and include only forces that act directly on it. With negligible air resistance, the only force is weight (mg) acting downward due to Earth's gravitational pull. Choice A incorrectly includes an 'upward force due to the ball's upward motion,' but motion is not a force—it's a state that results from previous forces. The ball moves upward because it was thrown (past force), but once released, only gravity acts on it, causing it to slow down. The essential strategy is to distinguish between forces (interactions happening now) and motion (result of past forces), and remember that projectiles in flight experience only gravitational force when air resistance is negligible.
A 1.0kg block hangs at rest from a vertical rope. The block is not accelerating. Air resistance is negligible. Which forces act on the block?
Select the correct free-body diagram.
Explanation: This problem requires identifying forces in a free-body diagram for a block hanging at rest from a rope. When drawing a free-body diagram, we choose the block as our object and include only forces that act directly on it. The forces are: weight (mg) acting downward due to Earth's gravity and tension acting upward from the rope supporting the block. Choice D incorrectly adds a 'force of motion' upward, but the block isn't moving—it's at rest—and even if it were moving, motion is not a force. Since the block is not accelerating, the net force is zero, meaning tension and weight are equal in magnitude but opposite in direction. The fundamental strategy is to identify forces from physical interactions (gravity from Earth, tension from rope) and recognize that equilibrium means balanced forces, not additional 'equilibrium forces.'
A 0.50kg block hangs at rest from a vertical spring. Air resistance is negligible. Which forces act on the block?
Explanation: This problem tests understanding of forces on an object in equilibrium attached to a spring. To draw a free-body diagram, we select the block as our system and identify forces acting directly on it. The block experiences two forces: its weight (mg) pulling downward due to gravity, and the spring force (elastic force) pulling upward. Since the block hangs at rest, these forces must be equal in magnitude and opposite in direction, resulting in zero net force. Choice B incorrectly adds a "force of rest" - being at rest is not a force but rather a state resulting from balanced forces. When an object is attached to a spring in equilibrium, the spring force exactly balances any other forces acting on the object.
A 0.20 kg puck slides to the right across a horizontal air table. Friction is negligible. After being struck, it continues moving at constant velocity. Which forces act on the puck while it slides?
Stem: Which free-body diagram correctly represents the puck while it moves at constant velocity?
Explanation: This question assesses the skill of identifying forces and constructing free-body diagrams in AP Physics 1. Isolate the puck as the system and consider its interactions while sliding. The only forces are the gravitational force mg downward from Earth and the normal force upward from the air table. Since friction is negligible and velocity is constant, there are no horizontal forces, and the net force is zero in both directions. Choice A is incorrect because it includes a force to the right due to motion, but constant velocity does not require a sustaining force; that's a misconception from Aristotelian thinking. Always remember that for objects in uniform motion, free-body diagrams should show balanced forces, with no 'momentum force' or 'force of motion' included.
A 5.0 kg box sits at rest on a horizontal floor. A student pushes it horizontally to the right with 8.0 N, but it does not move. Static friction is present. Which forces act on the box?
Stem: Which free-body diagram correctly represents the forces on the box?
Explanation: This question assesses the skill of identifying forces and constructing free-body diagrams in AP Physics 1. Choose the box as the system and identify all external forces acting on it. The forces include the gravitational force mg downward from Earth, the normal force upward from the floor, the applied push of 8.0 N to the right from the student, and static friction to the left from the floor opposing the push and preventing motion. Since the box remains at rest, static friction equals the push in magnitude but opposite in direction, maintaining equilibrium. Choice D is incorrect because it includes a force left exerted by the box on the student, but free-body diagrams only show forces on the system, not forces exerted by the system on other objects, per Newton's third law. To avoid errors, focus solely on forces acting on the chosen object and use Newton's laws to infer magnitudes when needed.
A block is held at rest against a vertical wall by a horizontal push to the right. Static friction is present. Which forces act on the block?
Explanation: This problem involves analyzing forces on a block held against a vertical wall. To create a free-body diagram, we select the block as our system and identify all forces acting on it. The block experiences four forces: weight (mg) downward, the applied horizontal push to the right, the normal force from the wall pushing back to the left, and static friction acting upward to prevent the block from sliding down. Since the block is at rest, all forces must balance - the push equals the normal force horizontally, and friction equals weight vertically. Choice D incorrectly shows friction pointing downward, which would cause the block to accelerate downward rather than remain at rest. When an object is held against a vertical surface, friction acts to prevent sliding in the direction gravity would cause motion.