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dragon_122
Dec 31, 2007, 08:27 PM
I need help for my phy test!

The question goes like this,

A car of mass 800kg has an engine which deliver a power of 160kW. What is the minimum time which the car can be accelerated from rest to 20m/s?

terryg752
Dec 31, 2007, 11:37 PM
Points to remember:

Power = Work per unit time

Work = Change in kinetic energy

In this case:

Change in Kinetic Energy = 1/2 m v^2 (m = 800, v = 20)

= 160000

Work done = Change in Kinetic Energy = Power times time

Let time = t

Power = 160K = 160000 Jouls per second

Suppose time required = t

Power times time = 160000 t = Change in Kinetic Energy = 160000

t = 1