Q87 / 270 · NDA 2019 (Phase 2) · General Ability

A rigid body of mass 2 kg is dropped from a stationary balloon kept at a height of 50 m from the ground. The speed of the body when it just touches the ground and the total energy when it is dropped from the balloon are respectively. (acceleration due to gravity $=9.8 \mathrm{~m} / \mathrm{s}^2$ )

  • A
    $980 \mathrm{~m} . \mathrm{s}^{-1}$ and 980 J
  • B
    $\sqrt{980} \mathrm{~m} \cdot \mathrm{~s}^{-1}$ and 980 J
  • C
    $980 \mathrm{~m} \cdot \mathrm{~s}^{-1}$ and $\sqrt{980} \mathrm{~J}$
  • Correct answer
    D
    $\sqrt{980} \mathrm{~m} \cdot \mathrm{~s}^{-1}$ and 980 J

Solution

Fitting the given values in equation for energy as (mgh) and Velocity $(\mathrm{v} 2)=\mathrm{u} 2+2$ as, the velocity will be Sqrt (980) $\mathrm{m} / \mathrm{s}$ and energy will be 980 J .

Hence, the correct answer is option: 'D'.

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