Q 11 :

A tennis ball is dropped on to the floor from a height of 9.8 m. It rebounds to a height of 5.0 m. Ball comes in contact with the floor for 0.2 s. The average acceleration during contact is ________ ms-2. [Given g=10 ms-2]               [2023]



(120)

vi=2ghi=2×10×9.8=14 m/s

vf=2ghf=2×10×5=10 m/s

|aavg|=|ΔvΔt|=240.2=120 m/s2



Q 12 :

A ball is dropped from a height of 20 m. If the coefficient of restitution for the collision between ball and floor is 0.5, after hitting the floor, the ball rebounds to a height of ________ m.          [2023]



(5)

We know h'=e2h

h'=(0.5)2×20 m=5 m