1. Define concurrent and non-concurrent forces, equilibrant and resultant.

2. What do you understand by the "Triangle law?"

3. Determine the magnitude and direction of the resultant of the 400- and 800-pound forces of Fig. 47.

4. Compute the magnitude and direction of the resultant of the 600- and 700-pound forces of Fig. 47.

Fig. 47.

5. Determine the values of the horizontal and vertical com-ponents of the 700-pound force of Fig. 47.

6. Determine the magnitude and direction of the resultant of the four forces acting through the center of Fig. 47; also of their equilibrant.

7. Compute the resultant of the four parallel forces represented in Fig. 47.

8. Find the resultant of the 300-, 400-, 500-, and 800-pound forces of Fig. 47.

9. Suppose that the truss of Fig. 48 is one of several used to support a roof, the trusses being 1G feet apart. What is the probable weight of each? What is the total roof load borne by each truss if the roofing weighs 18 pounds per sq. foot?

10. What is the total snow load for the truss if the snow weighs 20 pounds per square foot (horizontal) ?

11. Compute the total wind load for the truss of Question 9, when the wind blows 75 miles per hour.

12. Supposing that the right end of the truss of Fig. 48 rests on rollers, and that the left end is fastened to its support, compute the values of the reactions (a) when the wind blows on the left; (b) when it blows on the right, 90 miles per hour.

Fig. 48.

13. Construct stress diagram for the truss of Fig. 48 for the following cases:

(a) When sustaining dead load only as computed in answer to Question 9.

(b) When sustaining wind pressure on the left, the truss being supported as described in Question 12.

(c) When sustaining wind pressure on the right, the truss being supported as described in Question 12.

14. Make a complete record of the stresses as determined in answer to the preceding question for cases a, b and c, and for snow load as computed in answer to Question 10. Compute from the record the value of the greatest stress which can come upon each member due to combinations of loads, assuming that the wind and snow loads will not act at the same time.

15. Suppose that the truss of Fig. 49 is one of several used to support a roof, the trusses being 12 feet apart. What is the probable weight of a truss and that of the roofing supported by one truss, if the roofing weighs 15 pounds per square foot ?

16. Compute the apex loads for the truss of Fig, 49 for snow if it weighs 20 pounds per square foot (horizontal).