Calculating Power (College Board AP® Physics 1: Algebra-Based): Revision Note

Calculating power

• Power is defined as:

The rate at which energy changes with respect to time

• The energy change could be:

  • a transfer of energy into or out of a system

  • a conversion from one energy type to another within a system

• Average power is the amount of energy being transferred or converted, divided by the time taken for the transfer or conversion to occur

$P_{avg}=\frac{∆E}{∆t}$

• Where:

  • $P_{avg}$ = average power, measured in $\mathrm{W}$

  • $∆E$ = change in energy, measured in $\mathrm{J}$

  • $∆t$ = change in time, measured in $\mathrm{s}$

• The unit of power is the watt

  • $1\mathrm{W}=1\mathrm{J}/\mathrm{s}$

• Since work done, $W$, is equal to the change in energy of an object or a system due to a force, average power can also be calculated using:

$P_{avg}=\frac{W}{∆t}$