Chapter 3 - Motion in Two Dimensions - Learning Path Questions and Exercises - Exercises - Page 99: 52

a). $0.765m$ b). Had the cannon been accelerating, the ball would not have fallen into it.

a). Initial vertical velocity = 5 m/s. $v=u+at$ $0=5-9.8\times t$ $t=0.51 s$ Total time =$2\times 0.51=1.02 s$ So, horizontal distance in this time $=0.75\times 1.02=0.765m$ b). Had the cannon been accelerating, the ball would not have fallen into it. Because the distance traversed by both would be not same for both.