Question

23. A particle of mass m attached to the end of string
The particle rotates in a circle about O as shown.
of length / is released from the horizontal position.
When it is vertically below O, the string makes
contact with a nail N placed directly below O at a
distance h and rotates around it. For the particle
to swing completely around the nail in a circle,
​

Answer 1

Answer:

option 2

Explanation:

When particle moves then

Loss in gr. PE = Gain in KE

mgl = 1/2mv^2

v^2 = 2gl..............(i)

For motion along the verticle circle of radius r to be completed

At lowest point ,

v^2 greater than equal to 5gr

2gl greater than equal to 5gr

l must be greater than equal to 5r/2

l must be greater than equal to 5(l-h)/2

so we get h greater than equal to 3l/5

Hence second option is correct answer