physics question
posted by anonymous
A 2kg mass is attached to a 5.50m long string. The mass is pulled 30 degrees from its lowest point and then released. What is the initial height of the pendulum above its lowest point?
I think I should be solving for Lcos(theta), where L = 5.50 and theta = 30, but that gives me the wrong answer.
Why? What is the correct procedure, and how might I visualize it in terms of right triangles?

bobpursley
what is 5.5(1cos30) ? Draw the figure, goodness. you have a Lcos(theta) along the vertical, but that is not all the way down.

anonymous
Thank you! I drew the figure and see the differences in the length, but still why is it 1  cos30?

bobpursley
ok, goodness. it is 5.55.5cos30.

anonymous
oh wow, thanks. I see that.
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