Question

A stone of mass $m$ tied to a string of length $60cm$ is whirled in a vertical circle. If the total energy of the stone at the highest position is $250J$, what is the value of $m$? (in $kg$)

• A. $20$
• B. $19$
• C. $18$
• D. $17$

Answer 1

The correct option is D $17$

60 cm = 0.6 m

Total energy in vertical circular motion is given by

$E=5mgr/2$

$m=2E/5gr$

$E=2\ast 250/5\ast 9.8\ast 0.6=17Kg$