Question

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 (Taking $g =10 \,N\,kg ^{-1}$ )

• A. $0.5\,s$
• B. $1.0\,s$
• C. $\sqrt{\frac{2}{3}}\,s$
• D. $2.0\,s$

Answer 1

Answer: (B)

$1.0\,s$

Answer 2

Tension in the string $(T)=m \times g$
$=30 \times 10=300\, N$

$T-M g=M a$
From the figure $300-10 \times 10 a$
$\Rightarrow a=20 ms ^{-2}$
Thus, the maximum acceleration with
which the stone can be raised is $20 ms ^{-2}$
Given, $s=10 m$
and $u=0$
$\therefore 10=\frac{1}{2}(20) t^{2}$
$t=1\,s$