(a) Explain by an example what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass m placed at a height h above the surface of the earth.
(b) What is the difference between potential energy and kinetic energy?
(c) A ball of mass 0.5 kg slows down from a speed of 5 m/s so that of 3 m/s. Calculate the change in kinetic energy of the ball. State your answer giving proper units.
Answers
(a) Explain by an example what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass m placed at a height h above the surface of the earth.
Answer
Energy possessed by a body by virtue of its position is called potential energy.
Derivation:
Let us consider a body of mass m raised from the ground to the height h, the amount of work done against gravity is
W = F x h
But, F = mg, the weight of the body.
So, W = mgh.
(b) What is the difference between potential energy and kinetic energy?
Answer
The answer is in the above picture .....
(c) A ball of mass 0.5 kg slows down from a speed of 5 m/s so that of 3 m/s. Calculate the change in kinetic energy of the ball. State your answer giving proper units.
Answer.
M=0.5kg v(initial)=5m/s V(final)=3m/s
change in K.E=1/2×M×V×V-1/2×M×v×v
=1/2×0.5×9-1/2×0.5×25
=2.25-6.25
=-4kgm/ss
OR
HEY DEAR....!!
-Initial K. E = 1/2 mv^2
= 1/2 x 0.5 x (5) ^2 = 6.25
- final K. E = 1/2mv^2
= 1/2 x 0.5 x (3) ^2 = 2.25
change in K. E = 4 J