Question

A stone tied to one end of spring $80\,cm$ long is whirled in a horizontal circle with a constant speed. If stone makes $25$ revolutions in $14 \sec$, the magnitude of acceleration of stone is :

• A. $850 \,cm / s ^{2}$
• B. $996\, cm / \sec ^{2}$
• C. $720 \,cm / s ^{2}$
• D. $650 \,cm / \sec ^{2}$

Answer 1

Answer: (B)

$996\, cm / \sec ^{2}$

Answer 2

Time period $=\frac{\text { No. of revolutions }}{\text { time }}=\frac{25}{14}=1.79 \sec$ Now angular speed $\omega=\frac{2 \pi}{T}=\frac{2 \times 3.14}{1.79}=3.51\, rad / \sec$ Now magnitude of acceleration is given by $a=\omega^{2} l=(3.15)^{2} \times 80$ $=985.6\,cm / \sec ^{2}$ $=996 \,cm / \sec ^{2}$