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 m/s²)

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

Answer 1

Answer: (B)

Maximum tension in the string T = mg
= 30 x 10
= 300 N

T - mg = ma
From the figure
300 - 10 x 10 = 10a
$\therefore $ a = 20 m s^-2
Thus, the maximum acceleration with which the stone can be raised is 20 m s^-2.
Given, s = 10 m
and u = 0
$\therefore $ $1 0 = \frac{1}{2} \left(2 0\right) \left(\text{t}\right)^{2}$
$\Rightarrow $ t = 1 s