a 4.0 pendulum's bob starts swinging from a height of 2.5m as per figure. Assume the friction and air resistance are negligible.

Question

anonymous · Answer

What is the highest point it will reach at the end of the first swing?

anonymous · Answer

at what point is its PE equal to its to KE?

jamesj · Answer

Where's the figure?

jamesj · Answer

In this system, btw, energy is conserved.  

Hence the bob at the end of the pendulum will stop at the same height, on both sides.   If it didn't, and it stopped higher, energy was added; if it stopped lower, energy was lost.

mani_jha · Answer

Let the height at which K.E And PE are equal be x. 
P.E=mgx.
Total energy= mgh h=4(Conservation of energy)
Therefore, mgx=mgh/2
x=h/2

mani_jha · Answer

sorry h=2.5 not 4

jamesj · Answer

No, that's not right.  It's not that we must necessarily have 1/2 of the PE at the top of its swing.