Initially,a small 2.0-kg rock is whirling at the end of a very thin string in a circular path of radius 0.75 m on a horizontal frictionless surface,as shown in the figure.The initial tangential speed of the rock was 5.0 m/s.The string has been slowly winding around a vertical rod,and a few seconds later the length of the string has shortened to 0.25 m.What is the instantaneous speed of the mass at the moment the string reaches a length of 0.25 m?
A)3.9 m/s
B)9.3 m/s
C)15 m/s
D)225 m/s
E)75 m/s

Question

Initially,a small 2.0-kg rock is whirling at the end of a very thin string in a circular path of radius 0.75 m on a horizontal frictionless surface,as shown in the figure.The initial tangential speed of the rock was 5.0 m/s.The string has been slowly winding around a vertical rod,and a few seconds later the length of the string has shortened to 0.25 m.What is the instantaneous speed of the mass at the moment the string reaches a length of 0.25 m? 
A)3.9 m/s 
B)9.3 m/s 
C)15 m/s 
D)225 m/s 
E)75 m/s

Quizplus · Accepted Answer

The Answer of Initially,a small 2.0-kg rock is whirling at the end of a very thin string in a circular path of radius 0.75 m on a horizontal frictionless surface,as shown in the figure.The initial tangential speed of the rock was 5.0 m/s.The string has been slowly winding around a vertical rod,and a few seconds later the length of the string has shortened to 0.25 m.What is the instantaneous speed of the mass at the moment the string reaches a length of 0.25 m? 
A)3.9 m/s 
B)9.3 m/s 
C)15 m/s 
D)225 m/s 
E)75 m/s

Initially,a Small 2