A rocket is fired vertically from the earth with an acceleration of 2g, where g is the gravitational acceleration. On an inclined plane inside the rocket, making an angle θ with the horizontal, a point object of mass m is kept. The minimum coefficient of friction μ min between the mass and the inclined surface such that the mass does not move is: (a) tan θ (b) 2tan θ (c) 3tan θ (d) tan2 θ

Answer: (a). In the rocket frame, effective gravity geff = g + 2g = 3g (pseudo force acts downward). No slipping: m geffsin θ ≤ μ m geffcos θ; geff cancels. So the answer is (a) μmin = tan θ.

A rocket is fired vertically from the earth with an acceleration of… | JEE Main 2016 (9 Apr, Shift 1)

Q25JEE Main 2016 · 9 APR · SHIFT 1Medium

Friction on an Incline

A rocket is fired vertically from the earth with an acceleration of 2g, where g is the gravitational acceleration. On an inclined plane inside the rocket, making an angle $\theta$ with the horizontal, a point object of mass m is kept. The minimum coefficient of friction $\mu$ min between the mass and the inclined surface such that the mass does not move is:

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Answer: (a)

In the rocket frame, effective gravity $g_{eff} = g + 2g = 3g$ (pseudo force acts downward).
No slipping: $m g_{eff}\sin\theta \le \mu m g_{eff}\cos\theta$ ; $g_{eff}$ cancels.
So the answer is (a) $\mu_{min} = \tan\theta$ .

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