A cars engine produces 100 kW of power. How much work does the engine do in 5 seconds

Question

A cars engine produces 100 kW of power. How much work does the engine do in 5 seconds

Answer 1

Work = Power*Time

• Time = 5 seconds
• Power = 500kW = 500,000 watts, where a "watt" is defined as one joule of energy per second

 

Work = (500,000 watts)*(5 seconds) = 2,500,000 joules

Answer 2

Power is "energy per unit time" - so it is a measure of work rate. Work is power * time,

 

W= Pt

 

where W is Work, P is power, and t is time.

 

However, when you multiply P * t, watch your units - you will get (kW)*(seconds). You may be expected to convert this to the more standard kWhr (kilo-watt-hours).