Question

A frictionless track ABCDE ends in a circular loop of radius R. A body slides down the track from point A which is at a height h = 5 cm. Maximum value of R for the body to successfully complete the loop is

• A. 5 cm
• B. $\frac{15}{4}$ cm
• C. $\frac{10}{3}$ cm
• D. 2 cm

Answer 1

The correct option is D 2 cm

For the body to complete the rotation, the centripetal force should be equal to its weight. Therefore, $m{v}^2/r=mg$.
Apply conservation of energy and we get a condition for vertical looping as $h=\frac{5}{2}r,\therefore r=2cm$