Here’s what you need to know:

• Power in terms of energy
• Power in terms of force
• Kilowatt-Hours

Let’s get moving!

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What is Power?
Rate of energy usage.

Two objects may use the same amount of energy, but the one that requires LESS time to convert the energy to a useful output is MORE powerful.

Power can be expressed as the formula:
P = Work done/t
Where Work = Fd

Since work done = change in energy,
P = ΔE/t

TOTAL Power INPUT is equal to the USEFUL output + WASTEFUL output.
P =

Power is measured in Watts (W),
1W = 1Js^-1

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Power can also be expressed in terms of Force:
Power = Force x velocity

From P = W/t,
Since W = Fd,
P = Fd/t

Since d/t = velocity,
P = Fv

*Remember, just like Work,
Power is POSITIVE when force, displacement & velocity are in the same direction.
Power is NEGATIVE when force is opposing the displacement & velocity 9such as friction).

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What is a Kilowatt-Hour?
Energy expended when work is done at a rate of 1 kW for 1 hour.
kWh is another method to measure ENERGY.
It is equivalent to the unit of JOULES.

1 kWh = 1000 W x 1 hour
1 kWh = 1000 W x 3600 s
1 kWh = 3.6 x 10⁶ J

Electricity bills for houses are commonly measured in kWh, since the electrical energy spent in a common household would be too large to express easily in Joules.

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