Question

An astronaut with a mass of `75 kg` is floating in space. If the astronaut throws a `8 kg` object at a speed of `3/4 m/s`, how much will his speed change by?

Answer 1

`v_2=8cms^-1`

Explanation:

This is a case of conservation of momentum
So, that means `m_1\vec{v_1}=m_2\vec{v_2}`

Here, subscripts of `1` refer to the object while of `2` refer to the astronaut.
So that means, `m_1=8kg` `v_1=3/2ms^-1`, `m_2=75kg`, and since the direction of movement is parallel, `\hat{v_1}=\hat{v_2}`

so, the equation reduces to `cancel{8}^2*cancel{3}^1/cancel{4}^1=cancel{75}^(25)*v_2`
So, `v_2=2/25ms^-1`

Simplification gives you that small answer up there.