As we know that here no air resistance while ball is moving in air
So here we will say that
initial total energy = final total energy

here we know that
(as it will be on ground at initial and final position)
so we will say

since mass is always conserved
so we will say that final speed of the ball must be equal to the initial speed of the ball
so we have

Answer:
Please see answer in explanation
Explanation:
1. Since each molecule has three kinetic degrees of freedom (can move in three independent directions), the gas must have 3N DoFs.
2. Each molecule has the three kinetic degrees of freedom the monotonic atom has moving without rotating but it can also spin. There are three axes for it to spin around so we would expect three rotational degrees of freedom, but as were as above, the one about the diatomic molecule's axis doesn't count because of quantum. So we have two rotational DoFs and three kinetic, for a total of 5 per molecules. So the gas will have 5N DoFs.
3.When a spring vibrates it has two DoFs, its KE and its PE, so adding 1 vibration adds 2 DoFs per molecule, giving 7 per molecule and giving thegas 7N DoFs.