Question

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

• A. $20m{s}^{-2}$
• B. $10m{s}^{-2}$
• C. $9.9m{s}^{-2}$
• D. $8m{s}^{-2}$

Answer 1

The correct option is C $9.9m{s}^{-2}$

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

$\therefore$ Acceleration, $a=l\times {\omega }^2$

$⟹a=80\times {10}^{-2}\times {\left(\frac{14\times 2\pi }{25}\right)}^2$

$⟹a=9.9$ $m/s^2$