← Physics C: Mechanics syllabus

United StatesPhysics C: Mechanics

Unit 3: Work, Energy, and Power

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does conservation of mechanical energy let us solve problems, and how do we account for energy dissipated by non-conservative forces?

Topic 3.4 Conservation of Energy: apply conservation of mechanical energy for conservative systems, and extend the energy balance to include the work done by non-conservative forces.
A focused answer to AP Physics C: Mechanics Topic 3.4, covering conservation of mechanical energy in conservative systems, the work-energy bookkeeping when non-conservative forces such as friction dissipate energy, choosing a system and reference, and applying the energy balance to incline, spring and pendulum problems, with worked examples.
11 min answer →

How is potential energy defined for conservative forces, and how do we move between a force and its potential energy by integration and differentiation?

Topic 3.3 Potential Energy: define potential energy for conservative forces, relate force and potential energy by $F = -dU/dx$ , and use gravitational and elastic potential energy, including the general gravitational form.
A focused answer to AP Physics C: Mechanics Topic 3.3, covering conservative forces and potential energy, the relation $F = -dU/dx$ between force and potential energy, gravitational potential energy near a surface and the general $-GMm/r$ form, elastic potential energy, and reading equilibrium from a potential-energy curve, with calculus-based worked examples.
11 min answer →

What is power as the rate of energy transfer, and how do we compute average and instantaneous power from work, force and velocity?

Topic 3.5 Power: define power as the rate of energy transfer, distinguish average from instantaneous power, and compute it from $P = dW/dt$ and $P = \vec{F}\cdot\vec{v}$ .
A focused answer to AP Physics C: Mechanics Topic 3.5, covering power as the rate of energy transfer, average versus instantaneous power, the relations $P = dW/dt$ and $P = \vec{F}\cdot\vec{v}$ , and applying power to motors, vehicles and lifting, with calculus-based worked examples.
10 min answer →

What is the kinetic energy of a moving object, and how does it connect to the work done on the object through the work-energy theorem?

Topic 3.1 Translational Kinetic Energy: define translational kinetic energy, recognize it as a scalar that depends on the square of speed, and connect it to net work through the work-energy theorem.
A focused answer to AP Physics C: Mechanics Topic 3.1, covering translational kinetic energy as a scalar proportional to the square of speed, its frame dependence, the relation to momentum, and the work-energy theorem that links net work to the change in kinetic energy, with worked examples.
10 min answer →

How is work defined for constant and variable forces, and how do we compute it as a dot product and as an integral of force over displacement?

Topic 3.2 Work: define work as the dot product of force and displacement, compute the work done by a variable force as an integral, and interpret work as the area under a force-position graph.
A focused answer to AP Physics C: Mechanics Topic 3.2, covering work as the dot product of force and displacement, the sign of work, the work done by a variable force as the integral of force over displacement, work as the area under a force-position graph, and the work-energy theorem, with calculus-based worked examples.
11 min answer →