Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# Raindrops 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 - Physics

Sum

Raindrops 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.

#### Solution

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 = (- 30)^2/2 xx 10^-3 = 900/2 xx 10^3 = 4.5 xx 10^5 m/s2

Force, F = ma

⇒ F = 4 × 10−6 × 4.5 × 105 = 1.8 N

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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 5 Newton's Laws of Motion
Q 8 | Page 79