Question

Raindrops of radius $1$ mm and mass $4$ mg are 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 on the head, estimate the force excerted by each drop on head.

Answer 1

Radius = 1mm = 10^-3 m;

 m = 4mg= 4×10^-6; 

u= 30m/s; v =0. V^2- u^2 = 2as or

 a = -450× 10^3m/s^2 

retardation.F= ma = 4×10^-6× 450× 10^3 = 1.8N