The document describes four physics problems involving momentum and impulse: 1) A crash test of a car colliding with a barrier at 20 m/s to test passenger safety. Calculations are shown for momentum, impulse, deceleration. 2) A hammer hitting a nail with a force. Calculations are presented for change in momentum, impulse, and average force. 3) A toy train engine colliding with a stationary truck. Momentum and speed are calculated using conservation of momentum. 4) A diagram of a hydraulic braking system where force and pressure are used to slow wheels via pistons and oil.