Question

If an object with a mass of `2 kg` changes speed from `2 m/s` to `4m/s`, by how much does its kinetic energy change?

Answer 1

`12` Joules

Explanation:

Given: mass `= 2 kg`, changes speed from `2 m/s " to " 4 m/s`. Find the `Delta KE`

`KE = 1/2 mv^2`

`Delta KE = 1/2 mv_2^2 - 1/2 m v_1^2`

`Delta KE = 1/2 (2)4^2 - 1/2 (2) 2^2`

The units `1 (kg*m^2/s^2) = 1` Joule

`Delta KE = 16 - 4 = 12` Joules

Since the mass stays the same you could have simplified the equation by factoring:

`Delta KE = 1/2 m (v_2^2 - v_1^2)`

`Delta KE = 1/2 (2) (4^2 - 2^2)`

`Delta KE = 16 - 4 = 12` Joules