A boy is whirling a stone around his head by means of a string. The string makes
ID: 1703713 • Letter: A
Question
A boy is whirling a stone around his head by means of a string. The string makes on complete revolution every second, and the tension in the string is Ft. The boy then speeds up the stone, keeping the radius of the circle unchanged, so that the string makes two complete revolutions every second. The string is held parallel to the ground during rotation. What happens to the tension in the string?Can someone explain how they got the answer? The choices are;
A. The tension is unchanged
B. The tension reduces to half its original value
C. The tension increases to twice its original value
D. The tension increases to four times its original value
Explanation / Answer
tension T =Ft =mat =mr^2t .......(1) (since a=r^2)
according to problem 1 =2 rad/s and 2 =4 rad/s
from eq(1) , tension T ^2
T1/T2 =1^2/2^2
T1/T2 =(2/4)^2
T1/T2 =(1/4)
T2 =4T1
The tension increases to four times its original value
option D IS correct answer.
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