AP Physics C: Mechanics Practice Quiz: Newton's First Law
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 10 questions to check your progress.
Question 1 of 10
All Questions (10)
A) The system will come to a complete stop.
B) The system's velocity will remain constant.
C) The system will begin to move.
D) The system's position will not change.
Correct Answer: B
Content point 3 explicitly states that if the net force on a system is zero, its velocity will remain constant. This means it could be at rest (zero velocity) or moving at a constant speed in a straight line.
A) The configuration where a system's velocity is constant.
B) The state in which a system is observed from an inertial reference frame.
C) The configuration of forces such that the net force exerted on a system is zero.
D) The state in which all forces on a system are equal in magnitude.
Correct Answer: C
Content point 2 provides the direct definition of translational equilibrium as the configuration where the net force exerted on a system is zero, represented by the equation ΣF = 0.
A) The book's velocity is constant, therefore it is not in an inertial reference frame.
B) The book is at rest, which means no forces are acting on it.
C) The book's velocity is constant (zero), therefore it is in translational equilibrium.
D) A net force is required to keep the book at rest on the table.
Correct Answer: C
The book's velocity is constant (zero). According to content point 1 and 3, a constant velocity implies that the net force on the system is zero. Content point 2 defines a zero net force as translational equilibrium.
A) An inertial reference frame
B) Constant non-zero velocity
C) Translational equilibrium
D) A change in velocity
Correct Answer: C
Content point 2 explicitly states that translational equilibrium is the configuration where the net force is zero and provides the derived equation ΣFᵢ = 0.
A) It is not an inertial reference frame because the train is moving.
B) It is an inertial reference frame because Newton's first law is verified.
C) It is in translational equilibrium because the net force on the observer is zero.
D) It cannot be determined without knowing the train's speed.
Correct Answer: B
The suitcase's velocity is constant (zero relative to the train). Since there is no net horizontal force on the suitcase, Newton's first law is verified. Content point 4 defines a frame where this law is verified as an inertial reference frame. The fact that the frame is moving at a constant velocity is consistent with it being inertial.
A) When the system is in any reference frame.
B) When a single, constant force is exerted on the system.
C) When the system is in translational equilibrium.
D) When the system is not moving.
Correct Answer: C
Content point 1 states that velocity remains constant under specific conditions. Content point 2 defines translational equilibrium as the state of zero net force. Content point 3 links zero net force to constant velocity. Therefore, being in translational equilibrium is the condition for constant velocity.
A) The object is not being observed from an inertial reference frame.
B) The net force exerted on the system is not zero.
C) The object will eventually come to rest.
D) There is only one force acting on the object.
Correct Answer: B
This question requires applying the contrapositive of Newton's first law. The law states: 'If the net force is zero, then velocity is constant.' The logical contrapositive is: 'If the velocity is NOT constant (i.e., changing), then the net force is NOT zero.'
A) all objects are at rest.
B) the net force on every object is zero.
C) an observer would confirm that Newton's first law holds true.
D) the reference frame itself has a constant, non-zero velocity.
Correct Answer: C
Content point 4 provides the definition directly: 'An inertial reference frame is one from which an observer would verify Newton's first law of motion.' While an inertial frame can have a constant velocity (D), this is a characteristic, not the definition.
A) There are no forces acting on the puck.
B) The net force on the puck is in the direction of its velocity.
C) The puck is in a state of translational equilibrium.
D) The puck will naturally slow down over time.
Correct Answer: C
Since the puck's velocity is constant, Newton's first law (Content 3) dictates that the net force on it must be zero. The condition of having zero net force is defined as translational equilibrium (Content 2). Note that there are forces (gravity, normal force), but they sum to zero.
A) The elevator is an inertial reference frame because the pen's velocity is constant.
B) The elevator is in translational equilibrium.
C) The elevator is not an inertial reference frame because Newton's first law appears to be violated.
D) The elevator must be at rest.
Correct Answer: C
There is a net force (gravity) on the pen, yet its velocity remains constant (zero relative to the observer). This contradicts Newton's first law, which states that a net force should cause a change in velocity. According to Content 4, a frame where the law is not verified is not an inertial reference frame. (This scenario corresponds to an elevator in freefall).