Answers to MEEG 2003 Test Ib

1.

(a) T_AB = 260 lb
(b) A = 240i - 80k lb
(c) B = - 240i + 134.4j + 100.8k lb

2.

(a) M_A = - 630i - 540j - 180k N.m
(b) M_AB = - 120 N.m
(c) Since M_AB < 0, the action of F tends to tighten the joint at A.
(d) d_s1 = 9.43 m
(e) d_s2 = 2.12 m

3.

A. (b)
B. (e)
C. (d)
D. (a)

4.

A. The rigid-body principle states that any two opposite forces acting on a rigid body will have no effect on the condition of rest or motion of the rigid body if they have the same magnitude and the the same line of action. On the other hand, the principle of transmissibility states that the effect of a force on the condition of rest or motion of a rigid body will remain unchanged if the force is moved to act at another point on its line of action.

B. The moment of a force F about a point P is actually the same as the moment of this force F about a specific axis. This specific axis passes through the point P and is perpendicular to the plane that contains the point P and the line of action of the force F.