A ball is tied to the end of a length of string. A student holds one end of the

Question

A ball is tied to the end of a length of string. A student holds one end of the string and whirls it so the ball travels in a vertical circle. The string is always taut. The tension in the string is highest when the ball is _____.

A) at the bottom of the circle

B) at the top of the circle

C) descending from the top to the bottom of the circle

D) ascending from the bottom to the top of the circle

Another similar scenario

A ball is tied to the end of a length of string. A student holds one end of the string and whirls it so the ball travels in a vertical circle. First she whirls the ball at a very fast speed, and then she very gradually lowers the speed. Where is the ball most likely to be when the string begins to sag?

A) ascending at the midway point between the top and bottom of the circle

B)at the top of the circle

C)at the bottom of the circle

D)descending at the midway point between the top and bottom of the circle

Thanks in Advance!

A ball is tied to the end of a length of string. A student holds one end of the string and whirls it so the ball travels in a vertical circle. The string is always taut. The tension in the string is highest when the ball is _____.

A) at the bottom of the circle

B) at the top of the circle

C) descending from the top to the bottom of the circle

D) ascending from the bottom to the top of the circle

Another similar scenario

A ball is tied to the end of a length of string. A student holds one end of the string and whirls it so the ball travels in a vertical circle. First she whirls the ball at a very fast speed, and then she very gradually lowers the speed. Where is the ball most likely to be when the string begins to sag?

A) ascending at the midway point between the top and bottom of the circle

B)at the top of the circle

C)at the bottom of the circle

D)descending at the midway point between the top and bottom of the circle

Thanks in Advance!

Explanation / Answer

a)

Tension is highest at the bottom of the circle <-----answer

At the bottom, the tension - force of gravity equals the centripetal force

So, T - mg = mv^2/r

So, T = mg + mv^2/r <------ forces additive so maximum when at bottom

But at the top, T +mg = mv^2/r ==> T = mv^2/r - mg <----- subtractiive so lower at top of the loop

b)

The ball is most likely to sag at the top of the loop <-------answer

At the top, Tension, T = mv^2/r - mg <----- subtrctive so , chances of being 0 is high so the rope may sag

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