# moment

## 246 - System with couples and forces on it

**Problem 246**

Determine the resultant moment about point A of the system of forces shown in Fig. P-246. Each square is 1 ft on a side.

## Couples

Couple is a system of forces whose magnitude of the resultant is zero and yet has a moment sum. Geometrically, couple is composed of two equal forces that are parallel to each other and acting in opposite direction. The magnitude of the couple is given by

Where $F$ are the two forces and $d$ is the moment arm, or the perpendicular distance between the forces.

## 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.

## 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.

## 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.

## 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.

## 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.

## 228 Intercepts of the resultant force

**Problem 228**

Without computing the magnitude of the resultant, compute where the resultant of the forces shown in Fig. P-228 intersects the x and y axes.

## 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.

## 226 - Moment of force about different points

**Problem 226**

In Fig. P-226 assuming counterclockwise moments as positive, compute the moment of force F = 200 kg and force P = 165 kg about points A, B, C, and D.