Question

If an object with a mass of `2 kg` changes speed from `19m/s` to `20 m/s`, by how much does its kinetic energy change?

Answer 1

`39J`, increase

Explanation:

Kinetic Energy of an object is given by
`E_k=1/2 m v^2`, where `m` is the mass and `v` the velocity* of the body.
In the given question, if `v_i` and `v_f` are the final and initial velocities respectively
Change in kinetic energy `Delta E_k =1/2 m (v_f^2-v_i^2)`
Substituting given values
`Delta E_k =1/2 .2. (20^2-19^2)`

*Even though velocity is a vector quantity, Kinetic energy is a scaler quantity because `v^2` i a scaler quantity.