Question

A small ball describes a horizontal circle on the smooth inner surface of a cone. Speed of the ball at a height of 0.1 m above the vertex is

• A. 4 ms^-1
• B. 3 ms^-1
• C. 2ms^-1
• D. 1 ms^-1

Answer 1

Answer: (D)

1 ms^-1

Answer 2

Using $\frac{mv^{2}}{R}$ = cos θ and mg = R sin θ

we get tan θ = $\frac{gR}{v^{2}}$

or $\frac{R}{h} = \frac{gR}{v^{2}}i.e.,v = \sqrt{gh}$

or v = $\sqrt{10 \times 0.1} = 1ms^{- 1}$