Let’s solve this step by step.
We are told:
- Mass of the ball, m = 0.25 kg
- Gravity, g = 9.8 m/s² (we’ll use this unless told otherwise)
- Total mechanical energy is constant → TE = PE + KE at every point
- At point A (top), the ball starts from rest → so KE at A = 0
→ Therefore, total energy TE = PE at A
---
Step 1: Find Total Energy (TE) using Point A
At point A:
Height h = 10 m
PE_A = mgh = 0.25 × 9.8 × 10
= 0.25 × 98
=
24.5 J
Since it starts from rest, KE_A = 0
So TE = PE_A + KE_A = 24.5 + 0 =
24.5 J
This total energy stays the same at all points!
---
Step 2: Calculate for each point
We’ll use:
- PE = mgh
- KE = TE - PE = 24.5 - PE
---
Point A (h = 10 m)
PE = 0.25 × 9.8 × 10 =
24.5 J
KE = 24.5 - 24.5 =
0 J
---
Point B (h = 8 m)
PE = 0.25 × 9.8 × 8
= 0.25 × 78.4
=
19.6 J
KE = 24.5 - 19.6 =
4.9 J
---
Point C (h = 4 m)
PE = 0.25 × 9.8 × 4
= 0.25 × 39.2
=
9.8 J
KE = 24.5 - 9.8 =
14.7 J
---
Ground (h = 0 m)
PE = 0.25 × 9.8 × 0 =
0 J
KE = 24.5 - 0 =
24.5 J
---
✔ All calculations checked and consistent with conservation of energy.
Final Answer:
| Point | Gravitational Potential Energy | Kinetic Energy |
|---------|----------------------------------|----------------|
| A | 24.5 J | 0 J |
| B | 19.6 J | 4.9 J |
| C | 9.8 J | 14.7 J |
| Ground | 0 J | 24.5 J |
Parent Tip: Review the logic above to help your child master the concept of conservation of mechanical energy worksheet.
