(a) What do you understand by the kinetic energy of a body?
(b) A body is thrown vertically upwards. Its velocity goes on decreasing. What happens to its kinetic energy as its velocity becomes zero?
(c) A horse and a dog are running with the same speed. If the weight of the horse is ten times that of the dog, what is the ratio of their kinetic energies?
(a) Kinetic energy of a body is the energy due to motion.
(b) The kinetic energy of the body will be equal to zero as kinetic energy is directly proportional to the square of the velocity. Therefore, when a body is thrown vertically upwards, the kinetic energy becomes zero.
(c) Speed of horse = speed of dog = v
Weight of dog = m
Weight of horse = 10m
KE1 is the for dog = \(\frac{1}{2}\)mv2
KE2 is for horse = \(\frac{1}{2}\)mv2 = \(\frac{1}{2}\)(10m)v2
Ratio = KE1 : KE2 = \(\frac{10}{1}\)