- #1
PsychonautQQ
- 784
- 10
Homework Statement
A thin, uniform, 3.8kg bar, 80cm long has two 2.5 kg balls glued on at either end. It is supported horizontally by a thin, horizontal, frictionless axle passing through its centers and perpendicular to the bar. Suddenly the right hand ball becomes detached and falls off, but the other ball remains glued to the bar. Find the angular acceleration of the bar just after the ball falls off.
The Attempt at a Solution
So the net torque will just be m_ball*g*r because each side of the bar will cancel each other out. So if we set
m_ball*g*r = I(alpha) = m_ball*(r^2)*(alpha)
so
g/r = (alpha)
(9.8)/4 = (alpha)
and I get 24.5 which is wrong by a factor of 2/3 (correct answer is 16.333)
The question is asking for the bars angular acceleration and I'm giving It the balls, but wouldn't they be equal?