A sping balance is adjusted at zero. Elastic collisions are brought about by dropping particles of one gram each on the pan of the balance. They recoil upwards without change is their speeds. If the height of fall of particles is $ 2 $ meter and the rate of particle dropping is $ 100 $ per seconds, then the reading of the balance is -

Question

A sping balance is adjusted at zero. Elastic collisions are brought about by dropping particles of one gram each on the pan of the balance. They recoil upwards without change is their speeds. If the height of fall of particles is $ 2 $ meter and the rate of particle dropping is $ 100 $ per seconds, then the reading of the balance is -, $ 128 \mathrm{gm} \mathrm{wt} $., $ 1252 \mathrm{gm} \mathrm{wt} $., $ 625 \mathrm{gm} \mathrm{wt} $., $ 1.25 \mathrm{gm} \mathrm{wt} $.

MARKS App · Accepted Answer

Velocity of the particle after it has fallen 2m, v = 2 g h = 2 × 9.8 × 2 m / s When a particles rebound from the pan, change in its momentum = 2 m v If n particles fall per second, then force exerted = n .2 m v = 100 × 2 × 1 × 10 − 13 × 4 × 9.8 N = 100 × 2 × 1 × 10 − 3 × 4 × 9.8 g m w t 9.8 × 10 − 3 = 128 g m w t

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