Question

(c) A ball of mass 20 g falls from a height of 7 m. It rebounds from the ground to a height of 5 m .

Find : (i) The initial potential energy of the ball,

(ii) The K.E of the ball just before striking the ground

(iii) The K.E of the ball after striking the ground, and

(iv) The loss in K.E on striking the ground.​

Answer 1

Answer:

(i) Potential energy= mass×gravity×height

=0.02 × 9.8×7

=1.372 J

(ii) kinetic energy at the ground = potential energy at the height of 7m

=1.372 J

(iii) kinetic energy at the starting point= potential energy at height of 5m from the ground = mgh =0.02×5×9.8= 0.98J

(iv) loss in kinetic energy= 1.372- 0.98

=0.392J