Learning Goals
- Identify the forces acting on an object using a free-body diagram.
- Explain what balanced and unbalanced forces mean for an object's motion.
- Distinguish between net force = 0 (no change in motion) and net force ≠ 0 (acceleration).
Warm Up
Label the diagram
A skydiver is falling. Use the lesson to fill in the table below — write the name and direction of each labelled force on the free-body diagram.
| Label | Name of force | Direction |
|---|
| A | | |
| B | | |
| C | | |
| D | | |
Hint: A = weight/gravity (down) · B = air resistance (up) · C = net force direction · D = balanced point (terminal velocity)
Your Turn
True or False? Fix the false ones
Circle T or F for each statement. If the statement is false, rewrite it correctly on the line below.
Balanced forces always mean that an object is stationary (not moving).
Correct it:
Unbalanced forces cause an object to accelerate (change its speed or direction).
Correct it:
In a free-body diagram, a longer arrow means the force is acting in a longer direction.
Correct it:
A skydiver falling at terminal velocity has balanced forces acting on them.
Correct it:
Net force is calculated by adding all forces on an object, taking direction into account.
Correct it:
Show What You Know
1. A book is sitting still on a desk. Name the two forces acting on the book and explain why the book does not move.
Recall
2 marks
2. A tug-of-war team on the left pulls with 600 N and the team on the right pulls with 500 N. What is the net force, and which way will the rope move?
Recall
2 marks
Wrap Up
In one sentence, what was the main idea of this lesson?