A stone tied to a string is whirled in a horizontal circle at constant speed. Its acceleration is:
AZero, since the speed of the stone is constant
BAlong the string, pointing outward away from the hand
CTangent to the circle, in the direction of motion
DDirected toward the centre of the circle along the string
Answer & Solution
Correct answer: D. Directed toward the centre of the circle along the string
Uniform circular motion has centripetal acceleration $v^2/r$ directed toward the centre.