Q. A body crosses the topmost point of a vertical circle with critical speed. What will be its acceleration when the string is horizontal?
A) $g$
B) 2$\ g$
C) 3$\ g$
D) 6 g
Explanation
(c) The body crosses the top most position of a vertical circle with critical velocity, so the velocity at the lowest point of vertical circle $u = \sqrt{5gr}$
Velocity of the body when string is horizontal is
$v^{2} = u^{2} - 2gr = 5gr - 2gr = 3gr$
$\therefore\ \ $Centripetal acceleration $= \frac{v^{2}}{r} = \frac{3gr}{r} = 3g$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.