The Student Room Group

Conservation Of Energy In A Vertical Circle

http://imgur.com/a/9cJcO

I'm doing Q5 in the June 2009 M3 paper and according to the mark scheme, the energy of the system is this:

Ek0 + mgl cos(theta) = Ek1 + mgl(1/4)

(Where Ek0 is the initial kinetic energy, which is 0 because it's released from rest, and Ek1 is the kinetic energy when the angle is theta)

That makes no sense to me considering that the initial GPE should be mgl/4 since the angle is arccos(1/4) initially and then mglcos(theta) should be the GPE when the object is below the initial starting point after being released. Where am I going wrong here?
Sorry you've not had any responses about this. :frown: Are you sure you've posted in the right place? :smile: Here's a link to our subject forum which should help get you more responses if you post there. :redface:


Just quoting in Danny Dorito so she can move the thread if needed :wizard:

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