An ornament for a courtyard at a World's Fair is to be made up of four identical, frictionless metal spheres, each weighing 2√6 ton-wts . The spheres are to be arranged as shown, with three resting on a horizontal surface and touching each other; the fourth is to rest freely on the other three. The bottom three are kept from separating by spot welds at the points of contact with each other. Allowing for a factor of 3, how much tension must the spot welds withstand?
Answer :
Solutions (listed by author)
Michael A. Gottlieb (using forces) (pdf, 69K)
Michael A. Gottlieb (using virtual work) (pdf, 70K) [Geoff Wright gave me this idea. ―mg]