# Simple Mechanics confusing me:S

brandon26
A boy whirls a stone in a horizontal circle of radius 1.2 m and at height 1.7 m above ground level. The string breaks, and the stone flies horizontally and strikes the ground after traveling a horizontal distance of 10 m. What is the magnitude of the centripetal acceleration of the stone while in circular motion?

Mentor
Use the kinematics of projectile motion to find the initial speed of the stone. Then use that speed to calculate the centripetal acceleration.

brandon26
Doc Al said:
Use the kinematics of projectile motion to find the initial speed of the stone. Then use that speed to calculate the centripetal acceleration.

yes, I used V^2=u^2 + 2as , where V=0 and u is the speed to be found. But the answer comes out wrong.

Mentor
Try finding the time it takes for the object to fall. Then use that time to calculate the horizontal speed.

brandon26
Wicked. Got the answer right by working out the time. Thanx.
PS. i got the firwst answer wrong because I assumed that V= o , but that was false