Physics 197 Lecture Notes - Lecture 19: Statics, Net Force, Bicycle Wheel
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Static equilibrium: static equilibrium describes the state of a system with no net force or net torque. Important because most materials have a threshold" for how much force they can support before breaking: relevant in structures, materials, etc, example: a 120 cm wide sign hangs from a 5 kg, 200 cm long pole. A cable of negligible mass supports the pole. What is the maximum mass of the sign if the maximum tension the cable can support is 300 n: model: statics problem = =(cid:882), treat pole as a long, thin rod, visualize: m c. Imagine a person holding a spinning bicycle wheel about its axis (with the orthogonal rotational axis pointing vertically) while sitting on a frictionless stool that can spin. When the person rotates the wheel 180 , he begins to spin on the stool in the original direction of rotation. In this example, the only torque is internal, therefore angular momentum is conserved.