2. Problem No. 2: The horizontal platform ABCD weighs 60 lb and supports a 240-lb load at its center. The platform is normally held in position by hinges at A and B and by braces CE and DE. For this problem, assume that the brace DE is removed. a) Draw the free body diagram for the platform ABDC. How many unknowns are there in total? How many equations of equilibrium do you have? Is this problem statically determinate? Is the platform stable? b) Assume that the hinge at A does not exert any axial thrust (There is no reaction force in z direction at the hinge A). Determine the reactions at the hinges and the force exerted by the brace CE. N 2 ft B 3 ft. 4 ft E 300 lb X =======

Find the smallest value of P for which the crate in the Prob. 4.34 will be in equilibrium in the position shown. (Hint: A rope can only support a tensile force.)

The figure shows a three-pin arch. Determine the horizontal component of the pin reaction at A caused by the applied force P.

The uniform bar AB of weight W and length L is pinned to a sliding collar at A and to the sliding rod BD at B. The spring wound around rod BD has a stiffness k and is undeformed when rod AB is in the position =0. Determine the expression for the angle (other than =90 ) at equilibrium and investigate the stability of equilibrium for this position.

Draw the FBDs for the beam ABC and the segments AB and BC. Note that the two segments are joined by a pin at B. Count the total number of unknowns and the total number of independent equilibrium equations.

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The bent rod of negligible weight is supported by the ball-and-socket joint at B and the cables attached to points A and C. Find the forces in the cables and the magnitude of the reaction at B. Dimensions Figure P.5.39

Find the magnitude of the pin reaction at B caused by the weight W=80lb. Neglect the weights of the members.

The linkage is made of two homogenous bars of weights shown in the figure. Determine the horizontal force P required to hold the linkage in the position shown.

Draw the FBDs for the entire structure and the member BDE. Count the total number of unknowns and the total number of independent equilibrium equations. Note that the cable that supports the 1200-lb weight runs over a smooth peg at D.