40 2 A rectangular box is supported by balls and sockets at

40 2) A rectangular box is supported by balls and sockets at A and E and by a roller on a horizontal surface at B. Determine the reaction at 8 when a 60-lb vertical force s applied at the midpoint D of edge CE as shown. MacBook Pro 4 5 6 3

Solution

A roller always have a single reaction, and that acts in vertical direction, therefore at B there will be only one reaction in vertical direction, i.e. in y-axis. What it does is that it provides a reactive force, which can be either a pull or push but only in the y-direction.

The ball and socket joints has reactions in all three directions of x, y and z, therefore there can be 3 reaction each at A and E. But the moment is not resisted by such joints, so moment has to be zero at any corner of the box.