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Currently Playing: Rotational Dynamics_7.2

A uniform, 8.4 kg, spherical shell 50 cm in diameter has four small 2 kg masses attached to its outer surface and equal spaced around it. This combination of spinning about an axis running through the center of the sphere and two of the small masses. What frictional torque is needed to reduce its angular speed from 75 rpm to 50 rpm in 30 s? A thin, uniform, 3.8 kg bar, 80 cm long, has very small 2.5 kg balls glued on at either end, as shown below. It is supported horizontally by a thin, horizontal, frictionless axle passing through its center and perpendicular to the bar. Suddenly the right-hand ball becomes detached and falls off, but the other balls remains glued to the bar. Find the angular acceleration α of the bar just after the ball falls off. Will the angular acceleration remain constant as the bar continues to swing? If not, will it increase or decrease? Find the angular velocity ω of the bar just as it swings through its vertical position.