A waiter is balancing a large serving tray at rest on his arm. The tray is 50 cm long and the waiter’s arm supports the tray 15 cm from its right-hand end. The tray’s weight is 10 N, which is spread evenly along its length, and 20 cm from the left-hand end of the tray is a serving of food that has a weight of 20 N. The waiter uses his spare hand to push down on the right-hand end of the tray to keep the tray horizontally level. What magnitude force does the waiter’s arm supporting the tray apply to the tray? Round your answer to one decimal place.
A horizontal flagpole has a mass of 15 kg that is equally distributed along its 4 m length. The left-hand end of the flagpole is secured firmly into the wall of a building, and the right-hand end of the flagpole supports a flag of mass 5 kg. The flagpole is stable in its horizontal position. What is the magnitude of the torque produced by the flagpole’s wall mounting?
A seesaw consists of a horizontal plank of wood 5 m long, with its mass equally distributed along its length. The fulcrum of the seesaw is positioned at the center of the plank. A child of mass 28 kg sits at the right-hand end of the seesaw, and a larger child with a mass of 35 kg sits at the left-hand end. The seesaw tips down on the larger child’s end, and the larger child shuffles toward the seesaw’s fulcrum until it starts to rise again. The larger child must be less than a certain distance from the fulcrum for the seesaw to start to rise again. What is this distance?