CBSE-XI-Physics
05: Newton's Laws of Motion
- #8Raindrops of radius 1 mm and mass 4 mg are falling with a speed of 30 m/s on the head of a bald person. The drops splash on the head and come to rest. Assuming equivalently that the drops cover a distance equal to their radii on the head, estimate the force exerted by each drop on the head.Ans : Given:
Radius of a raindrop, r = 1 mm = 10-3 m
Mass of a raindrop, m = 4 mg = 4 × 10-6 kg
Distance coved by the drop on the head, s = 10-3 m
Initial speed of the drop, v = 0
Final speed of the drop, u = 30 m/s
Using `` a=\frac{{v}^{2}-{u}^{2}}{2s}``, we get:
`` a=\frac{-{\left(30\right)}^{2}}{2\times {10}^{-3}}=-4.5\times {10}^{5}m/{s}^{2}``
Force, F = ma
⇒ F = 4 × 10-6 × 4.5 × 105
= 1.8 N
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