AP Physics 1: Algebra-Based Practice Quiz: Forces and Free-Body Diagrams
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 16 questions to check your progress.
Question 1 of 16
All Questions (16)
A) An interaction between two objects or systems.
B) A property inherent to a single, isolated object.
C) The energy an object possesses due to its motion.
D) The rate of change of an object's position.
Correct Answer: A
Content point 1 explicitly states that a force is an interaction between two objects or systems. The other options describe different physical concepts like inertia, kinetic energy, or velocity.
A) As scalars listed next to the object.
B) As curved lines pointing towards the object's surface.
C) As vectors originating from a dot representing the center of mass.
D) As vectors originating from the points where the forces are applied.
Correct Answer: C
Content point 7 specifies that forces exerted on an object are represented as vectors originating from the representation of the center of mass, which is often simplified as a dot.
A) Mass and acceleration.
B) Magnitude and direction.
C) Energy and power.
D) Weight and mass.
Correct Answer: B
Content point 3 states that forces are vector quantities. The definition of a vector in physics is a quantity that has both a magnitude (size) and a direction.
A) Forces are vector quantities.
B) An object or system cannot exert a net force on itself.
C) A force is an interaction between two objects.
D) Free-body diagrams are useful tools for visualization.
Correct Answer: B
Content point 4 states that an object or system cannot exert a net force on itself. The rocket and its exhaust form a system. The rocket accelerates because it exerts a force on the exhaust gases (one object), and the exhaust gases exert an equal and opposite force back on the rocket (a second object), consistent with forces being an interaction between two objects.
A) To determine the final velocity of an object without considering forces.
B) To calculate the mass and density of an object.
C) To show the internal forces within an object.
D) To visualize external forces on an object to help write equations of motion.
Correct Answer: D
Content point 5 explains that free-body diagrams are tools for visualizing forces exerted on an object and for determining the equations that represent the physical situation (like Newton's Second Law, ΣF = ma).
A) The force the book exerts on the table.
B) The forces exerted on the book by its environment.
C) The force the book exerts on the Earth.
D) The internal forces holding the book's pages together.
Correct Answer: B
Content point 6 specifies that the free-body diagram of an object shows each of the forces exerted on the object by the environment. Forces exerted *by* the book are not included on the book's free-body diagram.
A) The force of gravity on the trailer.
B) The force exerted by the car on the trailer.
C) The force exerted by the trailer on the car.
D) The normal force from the road on the trailer.
Correct Answer: C
The free-body diagram for the trailer must only show forces exerted *on* the trailer by its environment. The force exerted by the trailer on the car is a force exerted *by* the trailer, and it would belong on the car's free-body diagram.
A) It shows the forces an object exerts on its surroundings.
B) It describes the forces exerted on an object or system by its environment.
C) It shows only the gravitational force and the net force.
D) It describes the velocity and acceleration of the object.
Correct Answer: B
This is a direct application of content points 2 and 6. A free-body diagram is used to describe and visualize the forces exerted on a specific object or system by its surroundings (the environment).
A) The gravitational force on A and the force of A on B.
B) The gravitational force on A and the force of the table on A.
C) The gravitational force on A and the force of B on A.
D) The force of B on A and the force of the table on B.
Correct Answer: C
The free-body diagram for block A must show all forces exerted on A by its environment. The environment for A consists of the Earth (exerting a gravitational force) and block B (exerting an upward normal force). The force of the table does not act directly on A.
A) Because the force of gravity is always stronger than a person's pull.
B) Because the person and their shoes form a single system that cannot exert a net external force on itself.
C) Because forces must be represented as vectors originating from the center of mass.
D) Because the interaction is with the ground, not the shoes.
Correct Answer: B
This is a classic example of the principle that an object or system cannot exert a net force on itself (content point 4). The upward pull on the shoes is an internal force within the person-shoe system, which is cancelled by the downward pull of the hands on the body.
A) One
B) Two
C) Three
D) Four
Correct Answer: B
Content point 1 defines a force as an interaction between two objects or systems. Therefore, a single force always involves a pair of interacting objects.
A) A single downward force vector.
B) A downward force vector and a forward force vector.
C) An upward force vector and a downward force vector that are equal.
D) No force vectors, as it is momentarily at rest vertically.
Correct Answer: A
The diagram shows forces exerted on the object by the environment. Once the ball leaves the hand, the only environmental force acting on it (if air resistance is neglected) is gravity, which acts downward. The motion of the object is not a force and is not drawn on the FBD.
A) The tension in the cord pulling up on the lamp.
B) The gravitational force from the Earth on the lamp.
C) The tension in the cord pulling down on the ceiling attachment point.
D) The force of the lamp pulling down on the cord.
Correct Answer: B
A free-body diagram of a system shows only external forces. For the lamp-cord system, the interactions between the lamp and cord are internal. The external forces are those from the environment: the gravitational pull from the Earth on both the lamp and cord, and the upward pull from the ceiling on the cord. Of the choices given, the gravitational force on the lamp is an external force.
A) They are scalar quantities representing energy.
B) They represent interactions between the object and its environment.
C) They must always sum to zero for the diagram to be correct.
D) They include forces the object exerts on other objects.
Correct Answer: B
This statement correctly combines multiple concepts. Forces are interactions (point 1) between the object of interest and its environment (point 6), and the free-body diagram is a tool to visualize these forces (point 5).
A) The force of gravity should not be included for a moving object.
B) Velocity is a vector, but it is not a force.
C) The normal force only exists for stationary objects.
D) The force from the engine is an internal force and should be excluded.
Correct Answer: B
A free-body diagram shows only the forces exerted on an object (point 6). Velocity describes the object's motion, but it is not a force itself and should not be included on the diagram.
A) Square.
B) Triangle.
C) Dot.
D) Circle.
Correct Answer: C
Content point 7 states that forces are represented as vectors originating from the representation of the center of mass, 'such as a dot'. This simplification is standard practice for free-body diagrams.