A small object of mass m, on the end of a light cord, is held horizontally at a distance r from a fixed support as shown. The object is then released. What is the tension in the cord when the object is at the lowest point of its swing?

Options

A. (a)`mgl2`
B. (b)`mg`
C. (c)`2 mg`
D. (d)`3 mg`

Answer

D

Explanation

Applying energy conservation, speed at lowest point `=sqrt(2 gr)`
`T - mg = (mv^2)/r = m/r (2 gr) implies T = 3 mg`.