Two identical balls of mass M are attached to the two ends of a thin rod of length L and negligible mass. The rod is nailed to a wall at the center making a pivot (so the force of gravity points down in this figure). A blob of putty with mass 1/4M is dropped onto one of the balls, hitting it with speed v and sticking to it. Assume the collision happens instantaneously (you can ignore external forces during the collision). The system will rotate through an angle before momentarily stopping. What is that angle? Hint: draw two pictures, one "a short time later" when the heavier ball+putty side is lower, a "later still" diagram when the ball+putty has swung around and is in the upper position. Extra credit (5 points): what is the condition on L for this problem to make sense? What happens if L is larger/smaller than this critical value? Putty wad Rotation axis
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First, we need to find the angular velocity of the system just after the collision. To do this, we can use the conservation of angular momentum. Before the collision, the angular momentum of the system is given by the linear momentum of the putty multiplied by the Show more…
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