Chapter 3 - Motion in Two Dimensions - Learning Path Questions and Exercises - Conceptual Questions - Page 96: 12

When the cannon is pushed so that it has a horizontal velocity, all the components, the ball inside the cannon also has the horizontal velocity. So when the ball is launched, the relative velocity of the ball w.r.t the cannon in horizontal direction is zero, and therefore the ball falls back into the cannon.

When the cannon is pushed so that it has a horizontal velocity, all the components, the ball inside the cannon also has the horizontal velocity. So when the ball is launched, the relative velocity of the ball w.r.t the cannon in horizontal direction is zero, and therefore the ball falls back into the cannon.