Chapter 9: Force and Laws of Motion

Q1. A 5 kg ball moving at 4 m/s hits a wall and bounces back at 2 m/s. Find the change in momentum.

Solution

∆p = m(v₂ - v₁) = 5(-2 - 4) = -30 kg m/s
Change in momentum = 30 kg m/s

Q2. State Newton's third law of motion with an example.

Solution

For every action, there is an equal and opposite reaction. Example: When you push a wall, the wall pushes you back with equal force.