In tennis, what is one effect of applying topspin to a ball according to the discussion of projectile motion?

• A. It makes the ball accelerate downward due to gravity.
• B. It has no effect on trajectory.
• C. It causes the ball to fall shorter and bounce higher.
• D. It increases air pressure at the bottom of the ball.

Answer: (C)

Topspin changes the ball’s flight through the air via the Magnus effect. When the ball spins forward, air flows around it in a way that creates a downward force on the ball. This extra downward push adds to gravity, so the ball dips faster and ends up landing sooner and closer to the shooter. At the moment of bounce, the spin causes the ball to grip the court more as it contacts the surface, transferring energy in a way that increases the vertical rebound, making the ball bounce higher. So the overall effect is that the ball falls shorter in its flight and bounces higher after impact.