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NEET 2004
Exam
NEET
Year
2004
Subject
Physics
Chapter
Work, Power and Energy

NEET 2004 · Physics · Work, Power and Energy

A ball of mass 2 ~kg and another of mass 4 ~kg are dropped together...

A ball of mass 2 kg2 \mathrm{~kg} and another of mass 4 kg4 \mathrm{~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:

Options

  1. A2+1\sqrt{2}+1
  2. B1:41: 4
  3. C1:21: 2
  4. D1:21: \sqrt{2}

Correct answer

C. 1:21: 2

Step-by-step solution

Let E1andE2E_1 and E_2 be the K.E. of two bodies. Then E1=12m1v12\quad E_1=\frac{1}{2} m_1 v_1^2 and E2=12m2v22E_2=\frac{1}{2} m_2 v_2{ }^2 \therefore \quad \frac{E_1}{E_2}=\frac{\frac{1}{2} m_1 v_1^2}{12\frac{1}{2} m_2 v^2}=m1v12m2v22The\frac{m_1 v_1^2}{m_2 v_2^2} Theinitial velocity of both the bodies are zero. ∴v2=2gh is same for both  bodies ∴E1E2=m1m2=24=12\begin{aligned} & \therefore \quad v^2=2 g h\text{ is same for both } \\ & \text{ bodies } \\ & \therefore \quad \frac{E_1}{E_2}=\frac{m_1}{m_2}=\frac{2}{4}=\frac{1}{2} \end{aligned}
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