Question

An astronaut with a mass of `80 kg` is floating in space. If the astronaut throws an object with a mass of `10 kg` at a speed of `7/5 m/s`, how much will his speed change by?

Answer 1

change in velocity of the astronaut will be `0.175m/s`

Explanation:

It should be solved by law of conservation of linear momentum.

The mass of the astronaut `m_1=80kg`
The mass of the object thrown `m_2=10kg`
The Initial velocity of the astronaut `u_1=0m/s`
The Initial velocity of the object `u_2=0m/s`
The Final velocity of the astronaut `v_1=?`
The Final velocity of the object `v_2=7/5m/s`

By law of conservation of linear momentum.

`m_1xxu_1+m_2xxu_2=m_1xxv_1+m_2xxv_2`
`=>80xx0+10xx0=80xxv_1+10xx7/5`
`=>v_1=-14/80=-0.175m/s`

So change in velocity of the astronaut will be `0.175m/s` opposite to the direction of motion of the object