An object of mass 4kg is released from rest at a height of 20m above the ground. Its velocity is 20m/s when it hits the ground, the object does not rebound, and the acceleration due to gravity is 10m/s².

Then the amount of energy that is converted into heat and sound will be_____.

Given, mass = 4kg, 

Height = 20m, 

Initial velocity (u) = 0    (since the object starts from the rest)
Final velocity (v) = 20 m/s

g = 10m/s²
When a body reaches the ground, it possesses only Kinetic Energy.
K.E.$=\frac{1}{2}{\mathrm{mv}}^2$
       $=\frac{1}{2}\times 4\times 20\times 20$

K.E.$=800\mathit{ J}$
According to the Law of conservation of energy, energy can neither be created nor destroyed but can transform from one form to another.
So, the body having a K.E. of 800J gets transformed into heat and sound energy.
Therefore, the amount of energy that is converted into heat and sound will be 800J.