Question

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

• A. $20m/s^2$
• B. $12m/s^2$
• C. $9.9m/s^2$
• D. $8m/s^2$

Answer 1

The correct option is C $9.9m/s^2$

$f=\frac{14}{25}$

Acc, $=r{\omega }^2$

$\omega =2\times \pi \times \frac{14}{25}$

Acc, $=80\times (2\pi {)}^2\times \frac{{14}^2}{{25}^2}$

$=\frac{990}{100}=9.9m{s}^{-2}$