Forces and Newton’s Laws: Question 9
Syllabus 1.5.1
A force acting on an object can change its speed, its direction of motion, or its shape (or some combination of these). Which of the following examples shows a force changing an object's shape only, without changing its speed or its direction of motion?
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Worked solution
Step 1: Recall the possible effects of a force
A force acting on an object can change:
- its speed (make it speed up or slow down),
- its direction of motion, or
- its shape (stretch, compress, bend or twist it).
An object that is not moving at all can still have a force acting on it that changes only its shape.
Step 2: Check each option
| Option | What happens | Effect of the force |
|---|---|---|
| A | Bicycle slows down, same straight line | Change in speed only |
| B | Ball starts moving in the direction kicked | Change in speed and direction |
| C | Ball compresses, stays still in the gymnast’s hand | Change in shape only |
| D | Satellite keeps constant speed, direction keeps changing | Change in direction only |
Step 3: Identify the correct option
Only in option C does the object stay still (no change in speed, no change in direction) while the force squeezing it changes its shape. This is the example of a force changing shape only.
Final answer
Option C. The gymnast squeezing the foam ball changes its shape, without changing its speed or direction.