A girl of mass 42.5 kg42.5\text{ kg}42.5 kg runs and jumps horizontally onto a stationary trolley.
The girl lands on the trolley with a horizontal velocity of 3.60 m/s3.60\text{ m/s}3.60 m/s.
State the relationship between momentum, mass and velocity.
The trolley has a mass of 2.50 kg2.50\text{ kg}2.50 kg.
Using ideas about conservation of momentum, calculate the combined velocity of the girl and trolley just after the girl lands on it.
The girl holds a heavy medicine ball as she stands on the stationary trolley. She then throws the medicine ball forwards.
Explain what happens to the girl and the trolley.