If it were possible to remove gravity and friction, think about what would happen to a football if it were tossed into the air. Assume the football is in a vacuum (no gravity or friction) and is continuously moving, which force(s) would be acting on the ball?
Answer
A
A force must be applied to it when it slows to a position of rest.
B
A force must be applied to it before it slows to a position of rest.
C
No force is needed; an object in motion stays in motion.
D
Many forces must act upon it to keep it in motion.
Explanation
With gravity and friction absent, no net force acts on the football. Newton’s first law says that an object already in motion continues moving at a constant velocity unless a net force changes its motion. Therefore, no force is needed to keep the ball moving, which matches “No force is needed; an object in motion stays in motion.”
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