Test Index

Laws of Motion

© examsnet.com
Question : 26
Total: 40
A stone of mass m tied to the end of a string revolves in a vertical circle of radius R. The net force at the lowest and highest points of the circle directed vertically downwards are : [Choose the correct alternative]
 Lowest Point  Highest Point
 (a) mg−T1   mg+T2
 (a) mg+T1   mg−T2
 (c)mg+T1−
(mv12 )
R
  mg−T2+
(mv12 )
R
 mg−T1−
(mv12 )
R
  mg+T2+
(mv12 )
R
T1‌and‌v1 denote the tension and speed at the lowest point. T2‌and‌v2 denotecorresponding values at the highest point
Solution:  
In the figure shown here L and H shows the lowest and highest points respectively.
At point L : T1 acts towards the centre of the circle and mg acts vertically downward.
∴ Net force on the stone at the lowest point in the downward direction =mg–T1
At point H : Both T2 and mg act vertically downward towards the centre of the vertical circle.
∴ Net force on the stone at the highest point in the downward direction =T2+mg
So option (a) is the correct alternative.
© examsnet.com
Go to Question:
Prev Question
Next Question