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Standard XII

Physics

Race of Rollers

A 60 kg boy...

Question

A $60 k g$ boy stands on a scale in the elevator. the elevator starts moving and records $450 N$ . Find the acceleration of the elevator. (Take $g = 10 m / s^{2}$ )

2.5 m s^{- 2}

upwards

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2.5 m s^{- 2}

downwards

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2.5 m s^{- 2}

in either direction

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none of these

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Solution

The correct option is A $2.5 m s^{- 2}$ downwards
The weight of the boy $= 60 \times 10 = 600 N$ which is greater than scale reading of elevation so it will move downward.
From FBD, $m a = m g - F$
or, $a = g - \frac{F}{m} = 10 - \frac{450}{60} = 2.5 m / s^{2}$
Therefore acceleration of elevator, $a = 2.5 m / s^{2}$ downward.

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A 60kg boy stands on a scale in the elevator. the elevator starts moving and records 450N. Find the acceleration of the elevator. (Take g=10m/s2)

The correct option is A 2.5ms−2 downwardsThe weight of the boy=60×10=600N which is greater than scale reading of elevation so it will move downward.From FBD, ma=mg−For, a=g−Fm=10−45060=2.5m/s2Therefore acceleration of elevator, a=2.5m/s2 downward.

A $60 k g$ boy stands on a scale in the elevator. the elevator starts moving and records $450 N$ . Find the acceleration of the elevator. (Take $g = 10 m / s^{2}$ )