CE 201 - Statics Lecture 8

Coplanar Force System All forces lie in the x-y plane. Each force can be resolved into its two rectangular components Fx and Fy. If the particle is in equilibrium, then,  F = 0 So,  (Fx i + Fy j) = 0  Fx i +  Fy j = 0 F1 F2 F3 F4 x y

For  F to be zero, both of x and y components must be equal to zero.  Fy = 0 These equations can be solved for at most two unknowns. If the solution of the equations resulted in producing –ve force value, then the direction of the force is opposite to the assumed one.

Procedure for Analysis Draw the free-body diagram of the particle. Include all known and unknown forces (magnitudes and directions). Assume unknown sense of forces. Apply equilibrium equations [  Fx = 0 and  Fy = 0 ]. If more than two unknowns need to be determined and the problem involves a spring, then in this case use [ F = k  s ].

Assignment 2 2- 88, 91, 96, 102, 104, 113, 116, 123, 132 3-14, 19, 21, 28, 31, 32, 33, 39, 40