1. The speed with which the ball hits the ground is 17.1 m/s
2. The magnitude of the average force of air resistance exerted on it is 0.77 N
1. How to determine the velocity with which the ball hits the ground
- Initial velocity (u) = 0 m/s
- Acceleration due to gravity (g) = 9.8 m/s²
- Height (h) = 15 m
- Final velocity (v) =?
v² = u² + 2gh
v² = 2gh
Take the square root of both side
v = √(2 × 9.8 × 15)
v = 17.1 m/s
2. How to determine the force
We'll begin by calculating the time to reach the ground. This is illustrated below:
- Acceleration due to gravity (g) = 9.8 m/s²
- Height (h) = 15 m
- Time (t) =?
h = ½gt²
15 = ½ × 9.8 × t²
15 = 4.9 × t²
Divide both side by 4.9
t² = 15 / 4.9
Take the square root of both side
t = √(15 / 4.9)
t = 1.75 s
Now we can determine the force. This can be obtained as illustrated below:
- Mass (m) = 149 g = 149 / 1000 = 0.149 Kg
- Initial velocity (u) = 0 m/s
- Final velocity (v) = 9 m/s
- Time (t) = 5 ms = 1.75 s
- Force (F) = ?
F = m(v –u) / t
F = 0.149(9 – 0) / 1.75
F = 0.77 N
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