Question

Consider a drop of rain water having mass 1 g falling from a height of `1 km`. It hits the ground with a speed of `50 m//s` Take `g` constant with a volume `10 m//s^(2)`. The work done by the
(i) gravitational force and the
(ii) resistive force of air is :
A. (i) -10 J (ii) -8.25
B. (i) 1.25 J (ii) -8.25
C. (i) 100 (ii) J 8.75 J
D. (i) 10 J (ii) -8.75 J

Answer 1

Correct Answer - D
`w_(g)+w_(a)=K_(f)-K_(i)`
`mgh+w_(a) =(1)/(2)mv^(2)-0`
`10^(-3) xx 10xx10^(3)+w_(a)=(1)/(2)xx 10^(-3) xx (50)^(2)`
`w_(a)=-8.75 J` i.e. work done due to air resistance and work done due to gravity =10 J