There is a ball of mass 320 g. It has 625 J potential energy when released freely from a height. The speed with which it will hit the ground is
- A. 62.5~m/s ✓
- B. 2.0~m/s
- C. 50~m/s
- D. 40~m/s
Correct Answer: A. 62.5~m/s
Explanation
By conservation of mechanical energy, Potential Energy = Kinetic Energy at the ground. 625 = \frac{1}{2}mv^2 \Rightarrow 625 = \frac{1}{2}(0.32)v^2 \Rightarrow v^2 = 625 / 0.16 = 3906.25. Thus, v = \sqrt{3906.25} = 62.5~m/s.
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