A student investigates how a toy ball bounces on a hard floor.
She drops the ball from different heights and measures the bounce height each time using a vertical metre rule. She then calculates the ratio: Ratio=Bounce heightDrop height\text{Ratio} = \frac{\text{Bounce height}}{\text{Drop height}}Ratio=Drop heightBounce height
The table shows her results:
| Drop height (cm) | Bounce height (cm) | Bounce height / Drop height |
|---|---|---|
| 150 | 90 | 0.60 |
| 120 | 84 | 0.70 |
| 90 | 72 | 0.80 |
| 60 | 54 | 0.90 |
| 30 |
The student predicts that the ratio of bounce height to drop height will be 1.00 (or 1:1) when the drop height is 30 cm. Suggest why she made this prediction.
Use ideas about energy to explain why this prediction cannot be correct for a real ball.
Suggest two improvements the student could make to her experiment to obtain more accurate or reliable results.
The mass of the toy ball is 80 grams.
Calculate the mass of the ball in kg.
Calculate the gravitational potential energy of the ball when it is held 1.20 m above the floor. Use your answer to (c)(i) and the equation: potential energy=mass×gravitational field strength×height\text{potential energy} = \text{mass} \times \text{gravitational field strength} \times \text{height}potential energy=mass×gravitational field strength×height (Gravitational field strength = 10 N/kg10\text{ N/kg}10 N/kg)