An object has a mass of 4 kg. The object's kinetic energy uniformly changes from 48 KJ to 320 KJ over t in [0, 12 s]. What is the average speed of the object?

1 Answer
Shwetank Mauria
Jan 15, 2017

Average speed is 227.46 m/s

Explanation:

Kinetic energy of an objeect of mass m kg. moving with a velocity of v m/s is given by 1/2mv^2 joules. Let the initial velocity is u and final velocity be v.

As the mass of the object is 4 kg. and initial kinetic energy is 48KJ or 48000J

We have 1/2xx4xxu^2=48000 i.e. u^2=24000 and u=sqrt24000=sqrt(40^2xx15)=40sqrt15=154.92 m/s

and as the mass of the object is 4 kg. and final kinetic energy is 320KJ or 320000J

1/2xx4xxu^2=320000 i.e. u^2=160000 and

v=sqrt160000=400 m/s

Hence average speed is (v+u)/2=(400+154.92)/2=554.92/2=227.46 m/s

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