Question

Parachutists whose chutes have failed to open have been known to survive if they land in deep snow. Assume that a 78.0-kgparachutist hits the ground with an area of impact of 0.30 m2 at a velocity of 55 m/s, and that the ultimate strength of body tissue is 5×105N/m2. Assume that the person is brought to rest in 1.0 m of snow.

Find the average force of the snow on the person per area of impact.

Express your answer using two significant figures.

Answer 1

Given is :-

mass of the parachutist m=78 kg

area of imact = 0.30 m²

initial velocity before impact u=55m/s

Distance travelled in snow before coming to rest s=1m

Now,

We find the acceleration, and then the force required to stop

By applying third equation of motion we get

by plugging all the values we get

which gives  

Thus the magnitude of the force applied by the snow is

This force will produce a stress of

This is the required Average force of the snow on the person per area of impact.

We can clearly see that the parchutist will escape serious injuries because it is less than the strength that body tissue can take.