Question

A body of mass 0.02Kg falls on a heap of sand from a height of 5m. Before reaching to its state

of rest body travels a distance of 5cm into the sand. Find the resistance offered by sand on the body.​

Answer 1

Answer:

20 N

Explanation:

The energy is lost to the sand, as resistance does work against kinetic energy.

So, Also kinetic energy before striking the ground is equal to potential energy at height 5m.

Therefore, 0.02x10x5= Fr x 5x10^-2 , where Fr is force of resistance.

So, Fr= 20N.

Answer 2

Answer: The kinetic energy ball possesses just before striking the sand is -

K.E.=mgh  

This energy is dissipated traversing a distance  s , within the sand. So the work done on the sand is -

W=F⃗ ∙s⃗  

The work done is same as the K.E. of the ball, so  W=mgh , while the displacement and force are in same direction so  F⃗ ∙s⃗ =Fs , we can equate the two -

mgh=Fs  

F=mghs  

Let's substitute the values and calculate -

F=0.02g5005  

F=2g   N

Hope it helps you!