GEN_ENG 205-2 HW5_WINTER 2026
Problem List
5.7, 5.20, 5.36, 5.47, 5.57, 5.60, 5.75, 5.87
DUE ON FRIDAY FEBRUARY 13, 2026, 8:00 am
Problem 5.7
A person holds a mass m with their arm extended horizontally. The mass m = 5 kg, and the mass of
his arm is mₐ = 3.6 kg. The angle α = 15°. Determine the force FD exerted by the deltoid muscle and
the components Sₓ and Sᵧ of the reaction at the shoulder joint.
Problem 5.20
The unstretched length of the spring CD is 350 mm. Suppose that you want the lever ABC to exert a
120-N normal force on the smooth surface at A. Determine the necessary value of the spring
constant k and the resulting reactions at B.
Problem 5.36
This structure, called a truss, has a pin support at A (a horizontal and vertical reaction force) and a
roller support at B (only a vertical reaction force), and is loaded by two forces. (Assume that the
weight of the structure is negligible.) The dimensions b = 0.25 m, h = 0.35 m. Determine the
reactions at the supports.
Strategy: Draw a free-body diagram treating the entire truss as a single object.
Problem 5.47
The suspended weights are each of mass m. The supports at A and E will each safely support a
force of 6 kN magnitude. Based on this criterion, what is the largest safe value of m?
Problem 5.57
The crane’s arm has a pin support at A. The hydraulic cylinder BC exerts a force on the arm at C in
the direction parallel to BC. The crane’s arm has a mass of 200 kg, and its weight can be assumed
to act at a point 2 m to the right of A. If the mass of the suspended box is 800 kg and the system is in
equilibrium, what is the magnitude of the force exerted by the hydraulic cylinder?
Problem 5.60
The weight W₁ = 1000 lb. Neglect the weight of the bar AB. The cable goes over a pulley at C.
Determine the weight W₂ and the reactions at the pin support A.
Problem 5.75
State whether each of the L-shaped bars shown is properly or improperly supported. If a bar is
properly supported, determine the reactions at its supports.
Problem 5.87
The force F acting on the boom ABC at C points in the direction of the unit vector 0.512i – 0.384j + 0.768k
and its magnitude is 8 kN. The boom is supported by a ball-and-socket at A and the cables BD and BE.
The collar at B is fixed to the boom.
(a) Draw the free-body diagram of the boom.
(b) Determine the tensions in the cables and the reactions at A.
0
