Question

A boy ties a stone of mass 100 g to the end of a 2 m long string and whirls it around in a horizontal plane. The string can withstand the maximum tension of 80 N.If the maximum speed with which the stone can revolve is k/π rev./min.The value of K is(Assume the string is massless and unstretchable)

• A. 400
• B. 300
• C. 600
• D. 800

Answer 1

Answer: (C)

600

Answer 2

T=$mw^2r$
⇒80=0.1×(2π×$\frac{K}{\pi}$×$\frac{1}{60}$)2×2
⇒$\frac{800}{2}$=$\frac{K^2}{900}$
⇒ K = 30 × 20 = 600
The correct option is (C) : 600