Exam: 286037RR

Exam: 286037RR - Engineering Mechanics, Part 2
1. The horizontal beam represented in Examination Figure 6 carries three loads P 1 , P 2 , and P , which act vertically downward and have the magnitudes and positions indicated. The beam rests on two supports at A  and B, which are so located that the horizontal distance between the lines of action of the reactions R  and R 2  is 24 ft. The magnitude of the reaction R
A. 15,220 lb.
B. 15,670 lb.
C. 14,330 lb.
D. 14,780 lb.
2. As indicated in Examination Figure 1, a wooden box containing several objects is supported on a horizontal surface. The total weight of the box and its contents is 150 lb. The horizontal force P required to start the box sliding along this surface is 60 lb. If additional objects weighing 50 lb were placed in the box, the magnitude of the horizontal force required to slide the box along the supporting surface would be A. 60 lb.
B. 70 lb.
C. 90 lb.
D. 80 lb.

3. A body that weighs 50 lb is placed in contact with an inclined plane surface. The coefficient of friction between the surfaces is 0.25 and the angle between the inclined surface and the horizontal reference plane is 28º. In order to keep the body from sliding, by using an applied force whose line of action is parallel to the inclined supporting surface, what is the least permissible magnitude of force?
A. 6.3 lb
B. 14 lb
C. 50 lb
D. 12.5 lb

4. A body that weighs 50 lb is placed in contact with an inclined plane surface. The coefficient of friction between the surfaces in contact is 0.25. If the angle between the inclined surface and a horizontal reference plane is 28º, and if the body is to be prevented from sliding by an applied force whose line of action is parallel to the inclined supporting surface, what is the least permissible magnitude of the force?
A. 12.5 lb
B. 1.25 lb
C. 125 lb
D. 0.125 lb

5. In Examination Figure 4, the magnitude of the force F and its direction along its line of action are
A. 28,800 lb away from P
B. 28,800 lb toward P
C. 24,400 lb toward P
D. 24,400 lb away from P

6. What equation is generally used when it is desirable to consider the resultant moment of the forces acting on a body at rest?
A. ∑F = 0
B. ∑F 1 = 1
C. ∑Z
D. ∑M

7. A body that weighs 50 lb is placed in contact with an inclined plane surface. The coefficient of friction between the surfaces in contact is 0.25. If the angle between the inclined surface and a horizontal reference plane is 28º, what would be the angle of repose for the body and the material used for the surface?
A. 17º 00'
B. 20º 00'
C. 14º 00'
D. 30º 00'

8. When solving a practical problem where the magnitudes of two forces are unknown, your calculations can be simplified if one of the reference axes coincides with the line of action of one of the unknown forces and the other reference axis is
A. equal to zero.
B. vertical to that line of action.
C. perpendicular to that line of action.
D. horizontal to that line of action.

9. As indicated in Examination Figure 5, a body having the shape of a rectangular prism is supported on a horizontal surface. The weight W of the body is 150 lb, and the body is acted upon by a horizontal force P whose magnitude and location are as shown. If the magnitude of the friction force is just sufficient to prevent sliding of the body along the supporting surface, the horizontal distance between the line of action
of the weight of the body and the line of action of the total vertical force N exerted on the body by the supporting surface would be
A. 1.50 ft.
B. 1.20 ft.
C. 2.00 ft.
D. 1.00 ft.

10. Assume that the conditions are the same as in Examination Figure 8 and question 15, except that the line of action of the force applied to push the body upward along the inclined surface is to be parallel to that surface instead of horizontal. The magnitude of the smallest inclined force that would start the body moving would be
A. 58 lb.
B. 70 lb.
C. 64 lb.
D. 54 lb.

11. For the beam in Examination Figure 9, the magnitude of the inclined reaction R
A. 3800 lb.
B. 3610 lb.
C. 4000 lb.
D. 4200 lb.

12. Examination Figure 9 represents a beam that is supported at A and B. The characteristics of the loads P1  and P  that are applied to the beam and the positions of their lines of action are as indicated. If it is assumed that the line of action of the reaction R2  at B will be vertical, the magnitude of that reaction would be
A. 3900 lb.
B. 3480 lb.
C. 3760 lb.
D. 3620 lb.

13. As indicated in Examination Figure 8, a body that weighs 80 lb is to be pushed upward along a plane surface that is inclined so that the angle between a horizontal reference line and the surface is 30º. If the coefficient of friction for the materials of the body and the inclined surface is 0.2, the magnitude of the smallest horizontal force P that would start the body moving (rounded off to the nearest pound) would be
A. 52 lb.
B. 70 lb.
C. 56 lb.
D. 34 lb.

14. As indicated in Examination Figure 7, a body that weighs 200 lb is to be supported on a plane surface, which is inclined so that the angle between a horizontal reference plane and the surface is 35º. If the coefficient of friction for the materials used for the body and the surface is 0.3 and the body is to be prevented from sliding down the surface by a force P whose line of action is parallel to the surface, the least magnitude of the force P (rounded off to the nearest pound) should be
A. 49 lb.
B. 115 lb.
C. 66 lb.
D. 82 lb.

15. The condition that must exist when a body is at rest is that the magnitude of the resultant of forces
acting on the body must be
A. external.
B. 20 percent.
C. dependent upon the incline.
D. 0.

16. A sign is suspended from a supporting frame in the manner indicated in Examination Figure 2. The frame consists of two vertical posts and a horizontal beam, with the sign suspended from this beam by means of two vertical bars. The total weight of the sign is 400 lb and the weight of each of the bars is 50 lb. If each of these bars carries one-half of the total weight of the sign, the force exerted by the left bar on the fixture is
A. 250 lb.
B. 200 lb.
C. 150 lb.
D. 225 lb.

17. Examination Figure 3 gives the dimensions of the parts of a bracket that supports a body with the aid of a vertical cable. The bracket is composed of a horizontal bar and an inclined bar, and these bars are rigidly fastened to the wall of the building by means of upper and lower fixtures. The weight of the body is 3000 lb, and the weights of the cable and the bars may be neglected. The magnitude of the reaction R exerted
by the lower fixture on the horizontal bar is
A. 1500 lb.
B. 2700 lb.
C. 2100 lb.
D. 3350 lb.

18. Examination Figure 4 represents a balanced system consisting of four concurrent forces F, and F 4. The positions of the lines of action of the forces are as shown. The line of action of F is vertical, and that of F4  is horizontal. The diagram also includes the magnitudes of the forces F and the directions of these two forces along their lines of action. The magnitude of the force F its line of action are
A. 30,200 lb away from P.
B. 19,780 lb away from P.
C. 19,780 lb toward P.
D. 30,200 lb toward P.

19. What will be the result when the applied horizontal force and the friction force form a couple, the lines  of action are parallel, and the magnitudes are equal?
A. They will act in the same direction.
B. They will create friction.
C. They will cause the body to rotate.
D. They will create a mutual force.

20. As indicated in Examination Figure 10, a body that is composed of the three parts AB, BC, and CD (which are rigidly connected to one another) is supported at the points A and B and is subjected to two loads P1 and P  whose characteristics and locations are as shown. If it is assumed that the line of action of the reaction R
A. 498 lb.
B. 578 lb.
C. 658 lb.
D. 738 lb.