Question

A stone ties to a rope is rotated in a vertical circle with uniform speed. If the difference between the maximum and minimum tension in the rope is $20N$, mass of the stone in $kg$ is:
($g=10{ms}^{-2}$)

• A. $1.0$
• B. $1.5$
• C. $0.5$
• D. $0.75$

Answer 1

Answer: (A)

$1.0$

Let the mass of the stone be $m$, and the angular speed with which it rotates be $\omega$.

Thus at the bottom most point,

$T_b-mg=m{\omega }^{2}l$

And at the top most point,

$T_t+mg=m{\omega }^{2}l$

$⟹T_b-T_t=2mg=20$

$⟹mg=10$

$⟹m=1kg$