Answer:
Due to Conservation of Energy just as the ball hits the ground it's potential energy is assumed zero
Therefore disregarding air resistance all energy is converted into potential energy.
So KE = PE
(5 J)
Answer:84Nm
Explanation:
force=400N
Distance=0.210m
Workdone=force x distance
Workdone=400 x 0.210
Workdone=84Nm
Answer:

Explanation:
Assuming the pith balls as point charges, we can calculate the repulsive force between them, using Coulomb's law:

We observe that the magnitude of the electric force is directly proportional to the product of the magnitude of both signed charges(
) and inversely proportional to the square of the distance(d) that separates them.
Replacing the given values, where k is the Coulomb constant:

Explanation:
"The burning of fossil fuels , oil and natural and power from nuclear power provide about 87% of the energy used in the world.
Coal, natural gas, petroleum and nuclear power are the major energy providers to the whole world. Till date we are heavily depend on them. They provide for about 87% of the total energy used in the world.