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

Answer:

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#.