A 10 kg stone is suspended with a rope of breaking strength 30 kg-wt. The minimum time in which the stone can be raised through a height 10 m starting from rest is (Take, `g = 10 N kg^(-1)`).

Options

A. 0.5 s
B. 1.0 s
C. `sqrt(2/3) s`
D. `2.0 s`

Answer

B

Explanation

Tension in the string `T = mg`
`= 30 xx 10 `
`= 300 N`

`T - Mg = Ma`
From the figure
`300 - 10 xx 10 = 10 a`
`therefore a = 20 ms^(-2)`
Thus, the maximum acceleration with which the stone can be raised is
Given, `s = 10 m`
And `u = 0`
`therefore 10 = 1/2 (20)t^2`
`implies t = 1 s`