A raindrop of mass 3.10 10-5 kg falls vertically at constant speed under the influence of gravity and air resistance

air-resistance

#1

A raindrop of mass 3.10 10-5 kg falls vertically at constant speed under the influence of gravity and air resistance. Model the drop as a particle.
(a) As it falls 55 m, what is the work done on the raindrop by the gravitational force? J
(b) What is the work done on the raindrop by air resistance? J

Answer:

Work done= force* displacement.
A) Force exerted by gravitational of earth, F=mg
as it is falling with constant speed, so there will be no resultant acceleration.
therefore, forces on rain drop particle are in equilibrium, i.e force on raindrop due to gravitation is equal to force on rain drop due to air resistance.
W= Mgd=(3.10*10^-5)9.8155=0.0167 J.
B) this is same work done on raindrop particle by air resistance exerted on it.
Wair=0.0167J.