Question

Two horizontal forces,

F: ?(3N)iˆ?(4N)jˆ and F: ??(1N)iˆ?(2N)jˆ

7 July 17, 1981, Kansas City: The newly opened Hyatt Regency is packed with people listening and dancing to a band playing favorites from the 1940s. Many of the people are crowded onto the walkways that hang like bridges across the wide atrium. Suddenly two of the walkways collapse, falling onto the merrymak- ers on the main floor.

The walkways were suspended one above another on vertical rods and held in place by nuts threaded onto the rods. In the origi- nal design, only two long rods were to be used, each extending through all three walkways (Fig. 5-24a). If each walkway and the merrymakers on it have a combined mass of M, what is the total mass supported by the threads and two nuts on (a) the lowest walkway and (b) the highest walkway?

Apparently someone responsible for the actual construction realized that threading nuts on a rod is impossible except at the ends, so the design was changed: Instead, six rods were used, each connecting two walkways (Fig. 5-24b). What now is the total mass supported by the threads and two nuts on (c) the lowest walkway, (d) the upper side of the highest walkway, and (e) the lower side of the highest walkway? It was this design that failed on that tragic night—a simple engineering error.

12

pull a banana split across a friction- less lunch counter. Without using a calculator, determine which of the

vectors in the free-body diagram of

:

(b) F 2. What is the net-force compo- nent along (c) the x axis and (d) the y axis? Into which quadrants do (e) the net-force vector and (f) the split’s ac- celeration vector point?

Answer 1