Question

A mass m is attached to the end of a rod of length l. The mass goes along a vertical circular path with the other end hinged at its centre. What should be the minimum velocity of the mass at the bottom of the circle so that the mass completes the circle?

Options

• `sqrt(5gl)`

• `sqrt(2gl)`

• `sqrt(3gl)`

• `sqrt(4gl)`

Answer 1

`underline(sqrt(4gl))`

Explanation:

As the mass is attached to the end of a rod, it does not stack. Therefore v = 0 at the highest point, from v² - u² = 2as

0 - u² = 2(-g) 2l

∴ u = `sqrt(4gl)`