1.

A 8kg stone tied at the end of a string 1 metre long is whirled in a vertical circle. At the instant when the string makes an angle theta with the vertical, the speed of the stone is `4ms^(-1)` and the tension in the thread is 104N. Then theta is.A. `0^(@)`B. `30^(@)`C. `60^(@)`D. None of these

Answer» Correct Answer - C
`T-mgcostheta=(mv^(2))/(r)`
or `104-8xx10costheta=(8xx4xx4)/(2)`
or `104-8costheta=64`
or `80costheta=104-64`
or `costheta=(40)/(80)=(1)/(2)`
:. `theta=60^(@)` .


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