Classical Mechanics
Power Calculator
Calculate power from force & velocity (P = Fv), work & time (P = W/t), or voltage & current (P = VI). Four modes.
Result
P = W/t = Fv = VI
Step-by-Step Solution
What is Power?
Power is the rate at which work is done or energy is transferred. A powerful machine does the same amount of work as a less powerful one but in less time. Power is measured in Watts (W), where 1 W = 1 J/s. It bridges the gap between work done (energy transferred) and how quickly that work happens.
P = W/t = Fv = VI
P = power (W) | W = work (J) | t = time (s) | F = force (N) | v = velocity (m/s) | V = voltage (V) | I = current (A)
💡 1 horsepower (hp) = 745.7 W. James Watt defined horsepower by measuring how much work a horse could do in a minute. He used this to market his steam engines as replacements for horses.
Real-World Applications
Power Stations
A 1 GW power station produces 1,000,000,000 J of electrical energy every second.
Car Engines
Engine power (kW or hp) determines top speed and acceleration. A 100 kW engine is about 134 hp.
Human Power
A fit cyclist sustains ~250 W. Tour de France riders produce ~400 W for hours. Peak sprinting: ~2,000 W.
Solar Panels
A 400 W solar panel produces that power in full sun. Daily energy = power × hours of sun.
Frequently Asked Questions
What is the difference between power and energy?
Power (W = J/s) is the rate of energy transfer. Energy (J) is the total amount transferred. A 2 kW kettle uses energy for as long as it runs: energy = power × time = 2,000 W × 180 s = 360,000 J = 0.1 kWh (costing about a penny).
What is a kilowatt-hour?
1 kWh = 1,000 W × 3,600 s = 3,600,000 J = 3.6 MJ. It is the unit used by electricity suppliers. A 100 W bulb running for 10 hours uses 1 kWh of energy.
How is mechanical power related to electrical power?
Both are measured in Watts. Electric motors and generators convert between the two forms. An electric motor with 90% efficiency: 1,000 W electrical in → 900 W mechanical out. The other 100 W is lost as heat.