You are given a pendulum composed of a 0.030 kg mass on the end of a 0.60 m long massless string. If the pendulum is moved 30° from the vertical and given an initial speed of 0.39 m/s tangent to the support string and away from the vertical, how much higher relative to the release point of the pendulum swing will the pendulum rise?
The Attempt at a Solution
Here is what I did. I found the velocity at the bottom of the swing.
1/2vf^2 = 1/2vi^2 + mgL(1-cosθ)
and I got vf= 1.3 m/s
Then I did the same thing again, except I set vi to 1.3 and vf = 0
1/2vi^2 = mgL(1-cosθ)
and find θ, which I got 31.1 then I subtracted Lcos30 by Lcos31.1 and got .005 m. The answer is incorrect, can anyone help? BTW I already cancelled out the mass in all the above work.