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JEE Main 2020 (5 Sep, Shift 2) · Acceleration Due to Gravity

Acceleration Due to Gravity question from JEE Main 2020 (5 Sep, Shift 2)

Q107JEE Main 2020 · 5 SEP · SHIFT 2Difficult

Acceleration Due to Gravity

The acceleration due to gravity on the earth’s surface at the poles is g and angular velocity of the earth about the axis passing through the pole is ω\omega. An object is weighed at the equator and at a height h above the poles by using a spring balance. If the weights are found to be same, then h is (h << R, where R is the radius of the earth)

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Answer: (a)

  1. At the equator: W1=m(g−ω2R)W_1 = m(g - \omega^2 R)
  2. At height hh above the pole (h≪Rh \ll R): W2=mg(1−2hR)W_2 = mg\left(1 - \frac{2h}{R}\right)
  3. W1=W2⇒ω2R=2ghRW_1 = W_2 \Rightarrow \omega^2 R = \frac{2gh}{R}
  4. h=R2ω22gh = \frac{R^2\omega^2}{2g}, so the answer is (a).
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