4H PROBLEMS 



PROBLEM i. RESULTANT OF CONCURRENT FORCES. 

 (a) Problem. Given the following concurrent forces : 



. 950 1700 750 2200 



1 i2o > 'v 315 ; 4; 5 



Forces are given in pounds. Required to find the resultant, R, by 

 means of a force diagram. Check by calculating R by the algebraic 

 method. Give all equations. Also construct check force polygon. 

 Give amount and direction of the resultant. Scale for force polygon, 

 i"= 400 Ibs. 



(b) Methods. Start P^ at point 4", 3^" (x, y, using lower 

 left-hand corner of the border as the origin of co-ordinates) and take 

 the forces in the order, P 19 P 2 , P s , P 4 , P 5 . Draw check polygon 



starting at the same point and drawing the forces in the order 

 p p p p p 



r 2) r 4> r 5> r 3) *! 



(c) Results. The resultant is a force R acting through the point 

 of intersection of the given forces, and is parallel to the closing line 

 in the force polygon. It will be seen that it is immaterial in what 

 order the forces are taken in calculating the resultant, R. In the alge- 

 braic solution the summation of the horizontal components of the 

 forces, including the resultant, R, are placed "equal to zero, and the 

 summation of the vertical components of the forces, including the 

 resultant, R, are placed equal to zero. Solving these equations we 

 have the value of 'R, and the angle 0, which R makes with the X-axis. 



PROBLEM la. RESULTANT OF CONCURRENT FORCES. 

 (a) Problem. Given the following concurrent forces: 



iSoo. looo t 1700 . p 75Q. p ?iop 



2 30 ' 3 3i5'- 4 2 4 o' 



Forces are given in pounds. Required to find the resultant, R, by 

 means of a force diagram. Check by calculating R by the algebraic 

 method. Give all equations. Also construct check force polygon. 

 Give amount and direction of the resultant. Scale for force polygon, 

 i" = 400 Ibs. 



