← Physics syllabus

United StatesPhysics

Unit 4: Linear Momentum

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does a force acting over a time interval change an object's momentum, and what is impulse?

Topic 4.2 Change in Momentum and Impulse: relate impulse to the change in momentum through J = F*t = Delta p, and read impulse as the area under a force-time graph.
A focused answer to AP Physics 1 Topic 4.2, covering impulse as force times time, the impulse-momentum theorem J = F*t = Delta p, impulse as the area under a force-time graph, and why extending the contact time reduces the force, with full worked examples.
10 min answer →

How do elastic and inelastic collisions differ, and which quantities are conserved in each?

Topic 4.4 Collisions: analyze elastic and inelastic collisions using conservation of momentum, and distinguish them by whether kinetic energy is conserved.
A focused answer to AP Physics 1 Topic 4.4, covering elastic, inelastic and perfectly inelastic collisions, the conservation of momentum in all collisions, the conservation of kinetic energy only in elastic collisions, and solving collision problems, with full worked examples.
11 min answer →

Why is the total momentum of a system constant when no net external force acts, and how is that principle used to solve problems?

Topic 4.3 Conservation of Linear Momentum: apply conservation of momentum to an isolated system, where the total momentum before equals the total momentum after an interaction.
A focused answer to AP Physics 1 Topic 4.3, covering conservation of linear momentum for isolated systems, the role of internal versus external forces, Newton's third law as the underlying reason, and applying momentum conservation to recoil and explosions, with full worked examples.
11 min answer →

What is linear momentum, how does it combine an object's mass and velocity, and how does it differ from kinetic energy?

Topic 4.1 Linear Momentum: define linear momentum as the vector product of mass and velocity, p = mv, and distinguish it from kinetic energy.
A focused answer to AP Physics 1 Topic 4.1, covering linear momentum as the vector quantity p = mv, its units and direction, how momentum differs from kinetic energy, and the total momentum of a system, with full worked examples.
9 min answer →