# An object has a mass of #6 kg#. The object's kinetic energy uniformly changes from #84 KJ# to # 12 KJ# over #t in [0, 6 s]#. What is the average speed of the object?

##### 1 Answer

Feb 27, 2017

#### Answer:

#### Explanation:

This is the equation for kinetic energy. It can be rearranged to give

We know the mass

We know that the energy at the end is

Now we have the initial and the final velocities.

Work out the average (of anything) by adding them all together and dividing by the total number of things. In this case, we only have two velocities, so: