- #1
mooncrater
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Homework Statement
There is a question that says:
A small bal of mass m is attached to the end of the string of length ##l=1m## whose other end is fixed. From its lower position, the ball is given a kinetic energy ##\frac {mgl}{5}##. Find the net acceleration (in ##m/s^2## ) of the ball at the instant when the string makes an angle ##\theta## of##37^{¤}##.
Homework Equations
##\frac {mgl}{5}=mgh+1/2mv^2##
The Attempt at a Solution
since at an angle 37 degrees the ball will cover a distance ##\frac {l}{5}## because of which the kinetic energy at this point is zero. This it's velocity at that point is also zero. So the net acceleration should be equal to ##g## I. E. ##10m/s^2## since the centripetal force is equal to zero. But the answer is ##6m/s^2## by taking ##gsin\theta##. But then ##gcos\theta## is gravity's component in the radial direction, why is it ignored?