Engineering Mathematics

moment of a force

233 A force creating counterclockwise and clockwise moments

Problem 233
In Fig. P-231, a force P intersects the X axis at 4 ft to the right of O. If its moment about A is 170 ft·lb counterclockwise and its moment about B is 40 ft·lb clockwise, determine its y intercept.
 

Three points in XY plane (A, B, and O)

 

232 Moment of a force about points O and B

Problem 232
In Fig. P-231, the moment of a certain force F is 180 ft·lb clockwise about O and 90 ft·lb counterclockwise about B. If its moment about A is zero, determine the force.
 

Three points in XY plane (A, B, and O)

 

231 Force P producing a clockwise moment about the origin

Problem 231
A force P passing through points A and B in Fig. P-231 has a clockwise moment of 300 ft-lb about O. Compute the value of P.
 

Three points in XY plane (A, B, and O)

 

230 Distance from truss member to truss joint

Problem 230
For the truss shown in Fig. P-230, compute the perpendicular distance from E and from G to the line BD. Hint: Imagine a force F directed along BD and compute its moment in terms of its components about E and about G. Then equate these results to the definition of moment M = Fd to compute the required perpendicular distances.
 

Symmetrical Truss

 

229 Y-coordinate of the point of application of the force

Problem 229
In Fig. P-229, find the y-coordinate of point A so that the 361-lb force will have a clockwise moment of 400 ft-lb about O. Also determine the X and Y intercepts of the line of action of the force.
 

Point of application of a force

 

227 - Moment of resultant force about a point

Problem 227
Two forces P and Q pass through a point A which is 4 m to the right of and 3 m above a moment center O. Force P is 890 N directed up to the right at 30° with the horizontal and force Q is 445 N directed up to the left at 60° with the horizontal. Determine the moment of the resultant of these two forces with respect to O.