Final answer:
The correct statement is (b) Net force causes change in motion, aligning with Newton's first law, which states an object's motion changes only with a net external force.
Step-by-step explanation:
Net Force and Motion
The correct statement is (b) Net force causes change in motion. This is because, according to Newton's first law of motion, an object will remain at rest or continue to move at a constant velocity unless acted upon by a net external force. Essentially, this means a net force is required not just to cause motion but to change the state of motion of an object, which might mean to accelerate, decelerate, or change direction.
For example, a soccer ball at rest on a field will not move until a player kicks it. The kicking action applies a net force, causing the ball to accelerate from a state of rest to motion. Similarly, if the ball is already in motion and then another force is applied (like another kick or friction from the ground), the net force causes a change in the ball’s velocity, either increasing, decreasing, or altering its direction.
Therefore, the key distinction is that it's not just any motion, but a change in motion, which translates to a change in velocity, as per Newton's second law. This can encompass starting, stopping, and changing direction, all involving acceleration.