AP Physics C: Mechanics Flashcards: Power
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
A motor does 500 J of work over 10 seconds. Which equation would you use to find the average power?
You would use the average power equation, $P_{avg}=\frac{\Delta E}{\Delta t}$, where $\Delta E$ is the energy transferred (equal to the work done).
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A motor does 500 J of work over 10 seconds. Which equation would you use to find the average power?
You would use the average power equation, $P_{avg}=\frac{\Delta E}{\Delta t}$, where $\Delta E$ is the energy transferred (equal to the work done).
Define average power and state its equation.
Average power is the total amount of energy transferred or converted divided by the time it took for the process to occur. The equation is $P_{avg}=\frac{\Delta E}{\Delta t}$.
State the equation for instantaneous power delivered by a constant force.
The instantaneous power delivered to an object by a constant force is the dot product of the force and velocity vectors: $P_{inst}=\vec{F}\cdot\vec{v}$.
How does the time interval, $\Delta t$, affect average power if the total energy transfer, $\Delta E$, is constant?
If the same amount of energy is transferred in a shorter time interval, the average power is greater. A longer time interval results in lower average power.
What is the equation for instantaneous power in terms of work?
The instantaneous power delivered to an object is the derivative of work with respect to time, given by the equation $P_{inst}=\frac{dW}{dt}$.
In the equation $P_{inst}=\vec{F}\cdot\vec{v}$, what component of the force contributes to the power?
Only the component of the constant force that is parallel to the object's velocity contributes to the instantaneous power.
A car moves at a constant velocity while the engine applies a constant forward force. Which equation for power is most appropriate to use?
The equation $P_{inst}=\vec{F}\cdot\vec{v}$ is most appropriate, as it directly relates the instantaneous power to the constant force and the object's velocity.
If a constant force is applied perpendicular to an object's velocity, what is the instantaneous power delivered by that force?
The instantaneous power is zero because the component of the force parallel to the velocity is zero, making the dot product $\vec{F}\cdot\vec{v}$ equal to zero.
What is power in terms of energy transfer?
Power describes the rate at which energy is transferred into, out of, or within a system.
What is the key difference between average power and instantaneous power?
Average power measures the rate of energy transfer over a time interval, while instantaneous power measures the rate of energy transfer at a specific moment in time.