Question

A small sphere is given vertical velocity of magnitude v₀ = 5m/s and it swings in vertical plane about end of massless string. If max. tension string can withstand is equal to twice of weight of sphere, then angle 'q' with vertical at which string will break is –

• A. cos^–1$\left( \frac{2}{3} \right)$
• B. cos^–1$\left( \frac{1}{4} \right)$
• C. 60⁰
• D. 30⁰

Answer 1

Answer: (B)

cos^–1$\left( \frac{1}{4} \right)$

Answer 2

T– mg cos q = $\frac{mv^{2}}{\mathcal{l}}$ ………(i)

mg l cos q = $\frac{1}{2}$mv² – $\frac{1}{2}$ mv₀² ………(ii)

T = 2 mg ………(iii)

\ cos q = $\frac{1}{4}$