Introduction:

In this scenario, a ball is moving with a speed of 20 m/s on a smooth surface. We need to determine the magnitude of change in velocity of the ball.

Explanation:

To calculate the change in velocity, we need to consider the concept of acceleration. Acceleration is defined as the rate of change of velocity. In this case, since the surface is smooth, there is no friction acting on the ball. Therefore, the only force acting on the ball is the force of gravity.

1. Initial Velocity:
The initial velocity of the ball is given as 20 m/s. This indicates that the ball is already in motion with a constant velocity.

2. Force of Gravity:
The force of gravity acts vertically downwards due to the gravitational pull. However, since the surface is smooth, the force of gravity does not affect the horizontal motion of the ball.

3. Constant Velocity:
Since there are no external forces acting on the ball in the horizontal direction, the ball will continue to move with a constant velocity of 20 m/s.

4. Change in Velocity:
As there are no forces causing the ball to change its horizontal velocity, the magnitude of change in velocity is 0 m/s.

Conclusion:

In this scenario, since the ball is moving on a smooth surface with no external forces acting on it, the magnitude of change in velocity is 0 m/s. The ball will continue to move with a constant velocity of 20 m/s.