The Situation:
Shyam stops a ball of 100g from a building of height 10m.

Given Information:
- Mass of the ball (m) = 100g = 0.1kg
- Height of the building (h) = 10m
- Acceleration due to gravity (g) = 10ms^-2

Finding the Kinetic Energy:
To calculate the kinetic energy (KE) of the ball at a height of 4m, we need to consider the conservation of mechanical energy.

At the top of the building, the ball has potential energy (PE) given by the formula:
PE = mgh

Where:
m = mass of the ball (0.1kg)
g = acceleration due to gravity (10ms^-2)
h = height of the building (10m)

So, at the top of the building, the potential energy of the ball is:
PE = 0.1kg * 10ms^-2 * 10m = 10J

As the ball falls from the top of the building, its potential energy is converted into kinetic energy. At a height of 4m, the potential energy of the ball is given by:
PE = mgh

Where:
m = mass of the ball (0.1kg)
g = acceleration due to gravity (10ms^-2)
h = height of the ball (4m)

So, at a height of 4m, the potential energy of the ball is:
PE = 0.1kg * 10ms^-2 * 4m = 4J

To find the kinetic energy at a height of 4m, we subtract the potential energy at 4m from the potential energy at the top of the building:
KE = PE(top) - PE(4m) = 10J - 4J = 6J

Therefore, the kinetic energy of the ball at a height of 4m is 6J.

Explanation of Total Mechanical Energy:
Total mechanical energy is the sum of potential energy and kinetic energy. In this scenario, the potential energy at the top of the building is 10J, and the kinetic energy at a height of 4m is 6J.

As the ball falls from the building, its potential energy decreases while its kinetic energy increases. The total mechanical energy of the ball remains constant throughout the motion, according to the law of conservation of energy.

So, in this case, the total mechanical energy of the ball is:
Total mechanical energy = Potential energy + Kinetic energy
Total mechanical energy = 10J + 6J
Total mechanical energy = 16J

The total mechanical energy of the ball remains constant at 16J throughout its motion, as long as no external forces, such as air resistance, are acting on it.

Conclusion:
- The kinetic energy of the ball at a height of 4m is 6J.
- The total mechanical energy of the ball remains constant at 16J throughout its motion.
- The ball's potential energy decreases as it falls, while its kinetic energy increases, maintaining the total mechanical energy.