(a) Derive an expression for kinetic energy of a body having mass m and moving with a velocity v.

(b) When velocity of a body is increased 5 times, what is the change in its kinetic energy ?

© Two masses m and 2m are dropped from heights h and 2h. On reaching the ground, which will have greater kinetic energy and why ?

(a) For derivation see above questions.

(b) Kinetic energy is given by the expression KE = 1/2 mv^2, therefore, if velocity is made 5 times KE will increase by 25 times.

© More the potential energy more will be the kinetic energy of the body when it falls. Hence, the body with mass 2m will have greater kinetic energy as it has more potential energy.