(Im translating this from another language, so if it doesn't make any sense, please let me know and ill try to do a better job.)
A metal ball (mass=120g) is hanging from a string (lenght=85cm). The ball is struck horizontally. When the angle of the swing reaches 125 degrees the ball starts to deviate from its circular path. What was the ball's initial velocity?
m=0.120kg, r=0.85m, θ=125°
I don't know what to put here. :l
The Attempt at a Solution
Here's what i came up with: Conservation of energy. Eki=Epf
I figured the max height, the ball reaches should be h=r+r*sin(35°) ⇒0.85m + 0.85m*sin(35°)=1.3375m
v=5.1227 m/s ≈ 5.1m/s
There, the answer i came up with. The answer section at the end of the book says the correct answer is 5.6m/s.
What am i missing?
P.S. I was told, that i should mention that im studying physics without a teacher.