Force and Momentum

Overview

This lesson introduces a new quantity, but it should still feel connected to the force and motion work that came before. Keep the idea of momentum as a way to describe “how hard it is to stop or change the motion” visible while you practise the equation.

What You Need to Know

• Keep the role of direction visible through the velocity term when using momentum.
• Compare objects with different masses and speeds so you see why both variables matter.
• Use simple trolleys, carts, or collision videos to introduce conservation of momentum in one dimension.
• Keep before-and-after tables organised so you can compare total momentum clearly.
• Build the idea that conservation is about the whole system, not just one object.

How to Work Through It

1. Start with a retrieval question on mass and velocity, then ask which moving object would be harder to stop.
2. Introduce momentum and practise straightforward p = mv calculations.
3. Use a simple collision example to show how total momentum is conserved in one dimension.
4. Finish with before-and-after momentum questions and short written explanations.

Check Your Understanding

• Check whether you can compare the momentum of two objects with different mass and speed values.
• Use a hinge question where you decide whether total momentum has been conserved in a simple interaction.
• Try one short calculation where you must find a missing speed or mass from momentum data.

Common Mistakes

• Treating momentum as depending only on speed. Keep mass visible in every comparison.
• Some assume each object keeps the same momentum before and after a collision. Revisit conservation of total system momentum instead.
• Sign or direction errors can appear even in one-dimensional problems. Keep a clear direction convention when needed.

Next Steps

• Use the practice questions and experiment resource to reinforce both calculation and interpretation.
• Carry the momentum-change idea into impulse and collision forces.