Question

An astronaut with a mass of `75 kg` is floating in space. If the astronaut throws a `5 kg` object at a speed of `8 m/s`, how much will his speed change by?

Answer 1

His speed change is -0.5 m/s.

Explanation:

Momentum is conserved.

Momentum before = momentum after

`(m_1 + m_2)*u = m_1*v_1 + m_2*v_2`

`(75 kg + 5 kg)*0 = 75 kg*v_1 + 5 kg*8 m/s`

`75 kg*v_1 = -5 kg*8 m/s`

`v_1 = (-5 kg*8 m/s)/(75 kg) = -0.533 m/s ~= -0.5 m/s`

I hope this helps,
Steve