Freefall

Overview

In this lesson, you will connect Newtonian ideas back to a familiar real-world situation.

What You Need to Know

• State that g is approximately constant near the Earth’s surface and use freefall to model motion where gravity is the only force acting.
• Contrast ideal freefall with real falling motion where drag acts through air or liquid.
• Use force diagrams to show how the balance between weight and drag changes as speed increases.
• Explain terminal velocity as the point where drag equals weight, so the resultant force and acceleration become zero.
• Link back to W = mg so you recognise weight as the downward force in the model.

How to Work Through It

1. Start with a prompt about why heavy and light objects do not always fall in the same way in air.
2. Work through freefall, g, and the role of weight as the downward force on the object.
3. Add drag and use force diagrams to explain how acceleration changes during a fall.
4. Finish with terminal-velocity explanations and short qualitative comparison questions.

Check Your Understanding

• Check whether you can explain what the forces are on an object in true freefall and how that differs from falling in air.
• Use a hinge question where you identify the stage of motion at which terminal velocity has been reached.
• Try one question that asks what happens to acceleration when drag increases during the fall.

Common Mistakes

• Thinking heavier objects must always fall faster. Keep the role of drag and shape explicit.
• Some assume terminal velocity means the forces disappear. Revisit that the forces balance rather than vanish.
• g can be confused with drag or with weight itself. Keep each quantity named clearly in diagrams.

Next Steps

• Set short force-diagram and explanation questions on freefall and terminal velocity.
• Carry the whole force-topic picture into revision and assessment.