Question

An engine performs 4000 joules of work in 10 seconds. what is its power output in kilowatts and in horsepower?

Answer 1

1 watt is the power of 1 joules of energy per 1 second of time .
4000 joules / 10 second = 4 kilowatts / 10 secs
= 0.40 kw seconds.
1 horsepower ( hp) watts 400 watts /745.7 (hp /w ) = 0.5364hp

Answer 2

Concept

• In physics, power is the amount of energy transferred or converted per unit time.
• In the International System of Units, the unit of power is the watt, equal to one joule per second.
• In older works, power is sometimes called activity.
• Power is a scalar quantity

Given

An engine performs 4000 joules of work in 10 seconds

Find

The power output of given engine in kilowatts and in horse power

Solution

The steps are as follow:

• Work = 4000 J
• Time = 10 sec
• Power = Work/Time = 4000/10 = 400 watt
• Power = 400/745.7 = 0.54 horsepower

Hence the power output of given engine will be 400 watt and 0.54 horsepower

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