Final answer:
The length of the ramp needs to change for ramps of different angles because it affects the height that the ball reaches.
Step-by-step explanation:
The length of the ramp needs to change for ramps of different angles because it affects the height that the ball reaches. A ramp with a steeper angle (a greater incline) will result in the ball reaching a greater height compared to a ramp with a smaller angle. This is because when the angle of the ramp increases, the force required to lift the ball against gravity also increases, allowing the ball to reach a higher point.