10.80. Set Up:The forces on the roof are shown in Figure 10.80. Vand Hare the vertical and horizontal forceseach wall exerts on the roof.Figure 10.80Solve:gives and givesBy Newton’s third law, the roof exerts a horizontal, outward force on the wall. For torque about an axis at the lowerend of the wall, at the ground, this force has a larger moment arm the higher the wall. The torque on the walls islarger for taller walls and the building with taller walls is in more danger of collapsing.10.81. Set Up:The thermal energy developed equals the decrease in kinetic energy of the system. The angularmomentum of the system is conserved. Solve:gives andand Reflect:Angular momentum is conserved because there is no external torque due to the force that pushes the shaftstogether, but the friction forces in the clutch mechanism do negative work and remove kinetic energy.10.82. Set Up:
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