Energy transfer rate
What is power in physics?
Power measures how quickly work is done or energy is transferred. The same amount of work produces greater power when completed in less time.
Formula
Power formula
PowerP = W ÷ t
- P is power in watts.
- W is work in joules.
- t is time in seconds.
Worked example
600 J of work is completed in 12 s
- Write the formula: P = W ÷ t.
- Substitute the values: P = 600 ÷ 12.
- Calculate the power: P = 50 W.
Rearranged equations
Solve for work or time
Work
W = P × t
Multiply power by positive time.
Time
t = W ÷ P
Divide work by non-zero power. Work and power must have matching signs.
Units
Standard SI units
Use joules for work and seconds for time. Convert other units before entering values.
One watt1 W = 1 J/s
Understanding results
What does a higher power value mean?
A higher power value means work is being completed faster. Two machines may perform the same amount of work, but the machine that finishes sooner has greater power.
Calculation limits
Important assumptions
- Time must be greater than zero.
- Power may be positive, negative, or zero when calculating work.
- Power cannot be zero when calculating time.
- Work and power must have matching signs when calculating time.
- The calculator does not automatically convert units.
Related tools
Continue analyzing mechanics
Use the Work Calculator to solve work, force, or distance.
Use the Kinetic Energy Calculator for motion energy, or use the Force Calculator for force, mass, and acceleration.
Questions and answers
Power calculator FAQ
What formula does the power calculator use?
It uses P = W ÷ t, where power equals work divided by time.
What is the SI unit of power?
The SI unit of power is the watt, written as W. One watt equals one joule per second.
Can power be negative?
Yes. Negative power can represent energy being removed from a system or work occurring in the opposite defined direction.
Can time be zero or negative?
No. This calculator requires time to be greater than zero.