Question

A stone is moved in a horizontal circle of radius $4\, m$ by means of a string at a height of $20\, m$ above the ground. The string breaks and the particle flies off horizontally, striking the ground $10 \,m$ away. The centripetal acceleration during circular motion is

• A. $6.25 \,ms ^{-2}$
• B. $12.5\, ms ^{-2}$
• C. $18.75 \,ms ^{-2}$
• D. $25 \,ms ^{-2}$

Answer 1

Answer: (A)

$ y =\frac{g x^{2}}{2 v^{2}}$
$ 20 =\frac{10\left(10^{2}\right)}{2 v^{2}} $
$ \Rightarrow v^{2} =25$
$ a_{c} =\frac{v^{2}}{R}=\frac{25}{4} $
$=6.25 \,m / s ^{2} $