Question

A sphere is suspended by a thread of length $l$. What minimum horizontal velocity has to be imparted the ball for it to reach the height of the suspension

• A. $gl$
• B. $2gl$
• C. $\sqrt{gl}$
• D. $\sqrt{2gl}$

Answer 1

Answer: (D)

$\sqrt{2gl}$

Answer 2

Kinetic energy given to a sphere at lowest point

= potential energy at the height of suspension

⇒ $\frac{1}{2}mv^{2} = mgl$

∴$v = \sqrt{2gl}$