Question

A physics student is performing a experiment in which she twirls rubber stopper at the end of a string around in a circle at nearly constant speed and tries to determine its acceleration. Which of the following single changes would enables her to most nearly double the acceleration of the rubber stopper?

• A. Double the speed of the rubber stopper.
• B. Use a string that is twice as long as the original string.
• C. Reduce the speed of the rubber stopper to half its original value.
• D. Use a string that is half as long as the original string
• E. Use a rubber stopper with twice as much mass as the original rubber stopper.

Answer 1

Answer: (D)

Use a string that is half as long as the original string

Due to constant speed , student is doing uniform circular motion so tangential acceleration is zero .

as the tangential acceleration is zero , therefore total acceleration will be equal to centripetal acceleration , which is

$a=v^2/r$

which can be doubled by using a string that is half as long as the original string .

$a^{\prime }=\frac{v^2}{\frac{r}{2}}=2a$