# Homework Help: Statics/Moments - Force perpendicular to slope?

1. Oct 6, 2012

### AndrewZzz

Determine the resultant moment at support points A and B due to the forces acting on the truss as shown.

Fx = F(cos∅), Fy = F(sin∅), M = F(distance)

Point A -88.98kN*m
Point B ?

I have no problem calculating most of the forces, but I'm lost when it comes to knowing what to do with the forces that are perpendicular to the sloped surfaces. Do I calculate X and Y components for them? Does it automatically turn into an X or Y component? When trying to calculate the moment on point B, is the 10kN multiplied by zero because it's on the same x-axis as the point, or is the 10kN a Y component? Some insight would be hugely appreciated.

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2. Oct 6, 2012

### bschwartz

Yes, for any forces that are at an angle, generate the x and y components of the force. And good catch, the 10kN force will be multiplied by zero because it is on the same x-axis as point B (when calculating the reaction at B). However, only the x-component of that force is neglected in the calculations, be sure to include the y-component.

3. Oct 6, 2012

### AndrewZzz

I figured it would still require the X and Y components! Which angle would I use to calculate those?

4. Oct 6, 2012

### bschwartz

The angle should be 45degrees so the x-component is 10cos(45) and the y-component is 10sin(45). At least I hope it is haha.