Introduction

Welcome to the FiveHive article for Unit 3.5 of AP Physics 1!

In this article, we will be going over power and describing the transfer of energy into, out of, or within a system.

As usual, we will only cover the topics included in the CED for unit 3.5.

Power

Power is defined as the rate at which energy is transferred or converted, using Watts (W) as its units. As such, average power uses the formula of $P_{avg}=\frac{\Delta E}{\Delta t}$. In this equation, the change in energy is divided by the time taken for that change in energy to get the average power. Since work represents the change in energy from a force, an alternative formula for average power is $P_{avg}=\frac{W}{\Delta t}$. For instantaneous power, only the component of force parallel to the velocity contributes to instantaneous power, and the applicable formula is $P_{\text{inst}}=F_{||}v=Fv\cos \theta$. Keep in mind that questions regarding power could also exist in a graphical form, where they provide you with a force - velocity graph.

Practice