# An object has a mass of #4 kg#. The object's kinetic energy uniformly changes from #24 KJ# to # 42KJ# over #t in [0, 9 s]#. What is the average speed of the object?

##### 2 Answers

#### Answer:

#### Explanation:

Let the rate of increase of kinetic energy with time be some

We have two conditions:-

1.

2.

from 1. & 2.

Average speed =

where

#### Answer:

#### Explanation:

Let rate of change of kinetic energy be

where

Integrating both sides with

where

To evaluate

We have expression for kinetic energy as

To evaluate

Equation (1) becomes

If

Given is

Average speed