13 For Equilibrium (balance) The sum of all torques around any point have to add up to zero.
14 Most doorknobs are placed on the side of the door opposite the hinges instead of in the center of the door.Why is this so?If a torque of ½ Nm is requiredto open a door, how much forcemust be exerted on a door knob.76 m from the hinges comparedto a door knob in the middle ofthe door, .38 m from the hinges?
15 Cilla is working out in the gym with a 2 kg mass that she holds in one hand and gradually lifts up and down. Will Cilla find in easier to lift the mass if she pivots her arm at the shoulder or at the elbow? If Cilla’s arm is .60 m long from her sholder to her palm and .28 m long from her elbow to her palm, how much torque must she produce in each case to lift he weight?
16 Leif and Joan are rearranging the heights of their book shelves and they remove one of the 2 kg .60 m long shelves by each holding one end. A 5 kg stack of books is piled up on the shelf .2 m from Leif. How much force must leif and joan each exert to hold the shelf level?
17 Out:How far from the axis of a teeter-totter would a 400 N person have to be to balance a 800 N person who is 2 meters from the axis?