An object has a mass of 6 kg. The object's kinetic energy uniformly changes from 120 KJ to 72 KJ over t in [0, 4 s]. What is the average speed of the object?

1 Answer
Jan 28, 2017

Average speed is 177.46 m/s.

Explanation:

As one Joule is equal to 1 kgm^2/s^2 and as such the object's kinetic energy changes from 120,000KJ to 72000KJ.

As kinetic energy KE is given by 1/2mv^2, velocity is given by sqrt((2KE)/m)

and initial velocity is sqrt((2xx120000)/6)=sqrt40000=200 m/s

and final velocity is sqrt((2xx72000)/6)=sqrt24000=154.92 m/s

and average speed is (200+154.92)/2=354.92/2=177.46 m/s.