A car drives around a flat circular track at constant speed. What provides the centripetal force?
AThe engine's forward push
BFriction between the tires and the road
CThe car's weight
DAir pushing the car inward
On a flat track, static friction between the tires and road surface provides the inward (centripetal) force that keeps the car on the curved path.
Question 2 True / False
An object can move in a circle at constant speed and still be accelerating.
TTrue
FFalse
Answer: True
Acceleration is any change in velocity, and velocity includes direction. Moving in a circle means constantly changing direction, so acceleration is always present even at constant speed.
Question 3 Short Answer
If you are swinging a ball on a string in a circle and the string breaks, what path does the ball follow?
Think about your answer, then reveal below.
Model answer: The ball flies off in a straight line tangent to the circle at the point where the string broke.
Without the centripetal force (string tension), the ball continues in a straight line in the direction it was moving at the instant the force was removed, as Newton's First Law predicts.