Chapter 9
1. (p.267 prob.10) A 70-kg adult sits at one end of a 10-m board, on the other end of which sits his 30-kg child. Where should the pivot be placed so the board (ignore its mass) is balanced?
2. (p.268 prob.18) Three boys are trying to balance on a seesaw, which consists of a fulcrum rock, acting as pivot at the center, and a very light board 3.6m long (Fig. 9-55). Two boys are already on either end. One has a mass of 50kg, and the other a mass of 35kg. Where should the third boy, whose mass is 25kg, place himself so as to balance the seesaw?
3. (p.269 prob.27) A traffic light hangs from a structure as shown in Fig. 9-60. The uniform aluminum pole AB is 7.5m long and has a mass of 8.0kg. The mass of the traffic light is 12.0kg. Determine the tension in the horizontal massless cable CD, and the vertical and horizontal components of the force exerted by the pivot A on the aluminum pole.