Laws Of Motion Question 8
Question 8 - 2024 (29 Jan Shift 2)
A stone of mass $900 g$ is tied to a string and moved in a vertical circle of radius $1 m$ making $10 rpm$. The tension in the string, when the stone is at the lowest point is (if $\pi^{2}=9.8$ and $g=9.8 m / s^{2}$ )
(1) $97 N$
(2) $9.8 N$
(3) $8.82 N$
(4) $17.8 N$
Show Answer
Answer: (2)
Solution:
Given that
$m=900 gm=\frac{900}{1000} kg=\frac{9}{10} kg$
$r=1 m$
$\omega=\frac{2 \pi N}{60}=\frac{2 \pi(10)}{60}=\frac{\pi}{3} rad / sec$
$T-mg=mr^{2}$
$T=mg+mr \omega^{2}$
$=\frac{9}{10} \times 9.8+\frac{9}{10} \times 1\left(\frac{\pi}{3}\right)^{2}$
$=8.82+\frac{9}{10} \times \frac{\pi^{2}}{9}$
$=8.82+0.98$
$=9.80 N$
