Work Energy and Power - Result Question 20
23. A ball of mass $2 kg$ and another of mass $4 kg$ are dropped together from a 60 feet tall building. After a fall of 30 feet each towards earth, their respective kinetic energies will be in the ratio of
(a) $1: \sqrt{ } 2$
(b) $\sqrt{ } 2: 1$
(c) $1: 4$
(d) $1: 2$
[2004]
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Answer:
Correct Answer: 23. (d)
Solution:
- (d)
Since height is same for both balls, their velocities on reaching the ground will be same.
$ \therefore \frac{K \cdot E_1}{K \cdot E_2}=\frac{\frac{1}{2} m_1 v_0^{2}}{\frac{1}{2} m_2 v_0^{2}}=\frac{m_1}{m_2}=\frac{2}{4}=\frac{1}{2} $
