Power

PowerAs a store manager, would you prefer to hire a clerk who could unload a truck in one hour, or a second clerk that could unload a truck in half an hour?

PowerIf the employees did the same amount of work unloading the truck, what was the

difference?

Power

Time

PowerPower – is the rate at which work is done

In other words, how fast or slow is the work done

PowerWatt is the unit for power

Power1 watt is equal to 1 joule of work done in 1 second

PowerMake note of units, if time is not in seconds, it must be converted.

Remember that W=Fd, so P= .If , then P=F*v.

(F*d)t

PowerIn physics, when you see the word power you should think: power is the energy used by the time it takes to do the work.

PowerThe watt was named after James Watt (1736-1819), the Scottish engineer who invented the steam engine. Another unit of power that is often used for engine power is the horsepower. Watt expressed the power of his engines as the number of horses an engine could replace. One horsepower is equal to 746 watts.

Who has more power?

P=w/t

P= (100*2)/1P= 200 W

P= (100*2)/10P= 20 W

A motor does 5,000 joules of work in 20 seconds. What is the power of the motor?

A motor does 5,000 joules of work in 20 seconds. What is the power of the motor?

W= 5,000 Jt= 20 sP= ?

P= 5,000/20P= 250 W

A machine does 1,500 joules of work in 30 seconds. What is the power of this machine?

A machine does 1,500 joules of work in 30 seconds. What is the power of this machine?

W= 1,500 Jt= 30 sP= ?

P= 1,500/30P= 50 W