A parachutist weighing 50 kg descends at a constant speed of 10 m / s. What is the work

A parachutist weighing 50 kg descends at a constant speed of 10 m / s. What is the work of the air resistance forces in 20 minutes of falling?

Given:

m = 50 kilograms – the weight of the parachutist;

g = 10 Newton / kilogram – acceleration of gravity;

v = 10 meters / second – the speed at which the parachutist descends;

t = 20 minutes = 1200 seconds – time span.

It is required to determine A (Joule) – the work of the resistance forces for the time interval t.

Since the parachutist descends at a constant speed, the force of air resistance will be equal to the force of gravity acting on the parachutist:

F = F gravity = m * g = 50 * 10 = 500 Newtons.

In time t, the parachutist will cover a path equal to:

L = v * t = 10 * 1200 = 12000 meters.

Then the work will be equal to:

A = F * L = 500 * 12000 = 6,000,000 Joules = 6 MJ.

Answer: the work of the resistance force will be equal to 6 MJ.