Question

What is the change in momentum that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s?

Answer 1

`2"kg m"/"s"` of momentum is lost.

Explanation:

We have to find `Deltap`, where `p` is the linear momentum.

The formula for momentum is `p=mv`, where `m` is the mass of the body and `v` its velocity.

We have `p_1` and `p_2`. `Deltap=p_2-p_1`.

The mass, `m`, does not change and is always `1"kg"`.

For `p_1`:

`v=4"m"/"s"`

So `p_1=1*4=4"kg m"/"s"`

For `p_2`:

`v=2"m"/"s"`

So `p_2=1*2=2"kg m"/"s"`

`Deltap=p_2-p_1``

`Deltap=2-4`

`Deltap=-2"kg m"/"s"`

Therefore `2"kg m"/"s"` of momentum is lost.