Final answer:
A ball's motion can be changed in both speed and direction by a single action, such as hitting it with a racket at an angle. This simultaneous change in speed and direction is due to a net external force that produces acceleration, satisfying the condition stated in the student's question. The correct option is:B. False.
Step-by-step explanation:
The student's question relates to how a ball's motion can be changed with respect to both speed and direction by a single action. To address this, we must understand that a change in motion is fundamentally a change in velocity, which includes changes in speed, direction, or both. This is because velocity is a vector quantity, meaning it has both magnitude (speed) and direction.
When you start a ball rolling and then cause it to change its speed and direction with one action, you are applying a net external force that produces an acceleration. For example, hitting the rolling ball at an angle with a racket would change both its speed and direction instantly, meeting the challenge described in the question.
Comparing with other motions:
- A car rounding a bend at a constant speed is changing direction, but not speed.
- A merry-go-round increasing from rest to a constant rotational speed is changing speed, but its points move in a circular path at a constant speed at any given instant.
- A pendulum swings back and forth changes both speed and direction during its motion, but the change is not instantaneous, it occurs over the course of the swing.
- A bowling ball rolls straight down a bowling alley, changing speed as it may accelerate due to gravity and friction but not changing direction unless it hits the pins or gutter. The correct option is:B. False.