## Question

A boy whirls a stone in a horizontal circle 2 m above the ground by means of a string 1.25 m long. The string breaks and the stone flies off horizontally, striking the ground 10 m away. What is the magnitude of the centripetal acceleration during circular motion? Take *g* = 10

### Solution

Given, *h* = 2 *m*, *R* = 1.25 *m* and horizontal distance *s* = 10 *m*. When the string breaks, the stone is projected in the horizontal direction, which means that there is no initial vertical velocity.

From

The horizontal distance travelled in time *t* is

Where *v* is the velocity of the stone in the horizontal direction which is the same as its velocity in circular motion.

Eliminating *t* from (i) and (ii) we get

Now, centripetal acceleration is

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