Forces and Momentum · Paper 1 — Free Physics HL Practice Questions

An astronaut of mass $70\text{ kg}$ is initially at rest relative to their spacecraft in deep space. The astronaut throws a toolkit of mass $2.0\text{ kg}$ directly away from the spacecraft a speed of $6.0\text{ m s}^{-1}$ relative to the spacecraft. What is the speed of the astronaut relative to the spacecraft immediately after throwing the toolkit?

A firefighter of mass $75 \text{ kg}$ jumps from a stationary platform and lands on a stationary safety mattress of mass $60 \text{ kg}$. The firefighter arrives at the mattress with a downward speed of $4.0 \text{ m s}^{-1}$ and immediately moves together with it. What is the speed of the firefighter and mattress immediately after landing?

A cyclist and bicycle of combined mass $80 \text{ kg}$ travel at $8.0 \text{ m s}^{-1}$ on a level road. The cyclist stops pedalling and coasts to rest in $20 \text{ s}$. Friction is the only horizontal force acting during coasting. What is the magnitude of the friction force on the cyclist and bicycle during this phase?