Problem

A portable tripod hoist for moving objects in and out of a manhole is shown. The hoist con...

A portable tripod hoist for moving objects in and out of a manhole is shown. The hoist consists of identical-length bars AB, AC. and AD that are connected by a socket at A and are supported by equal 8 ft length cables BC, BD, and CD to prevent ends B, C, and D of the bars from slipping. Cable FAE passes around a frictionless pulley at A and terminates at winch E, which is fixed to bar AB. Idealize points A and E to be particles where all bar and cable forces pass through these points. If the tripod is erected on level ground and is 7 ft high, and the object being lifted in the manhole weighs 300 lb.

(a) Determine the forces in bars AC and AD and in portion AE of bar AB.

(b) Determine the force in portion EB of bar AB.

Hint: Define an xyz coordinate system where the x and y directions lie in the plane defined by points B, C, and D. and where the x or y direction coincides with one of cables BC, BD. or CD. Then determine the coordinates of points B, C, and D. The x and y coordinates of point A are then the averages of the coordinates of points B, C, and D.