Sum of Forces in X and Y Directions - axis set up normally

[cdornz]

Being asked for the sum of forces in the X and Y directions and the axis are set up 'normally' so like a plus sign ( + ).

I attempted the first one and I think I did it correctly, but I'm not so sure about the second one.

 

[Doc Al]

The first one is fine. Where's your work on the second one?

Note: While a diagram is useful for reference, please type up your work right here in the thread. That helps people give you better help.

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[cdornz]

So I was looking through my notes, and I saw the equation V_x = Vcosθ and V_y = Vsinθ.

I'm not sure though that this is where i can put these equations to use, since i don't know the value of V. In looking at the angles, F1 is 60° from the x-axis going counterclockwise. I'm lost in more of how to put the information I do know together.

 

[Doc Al]

So I was looking through my notes, and I saw the equation V_x = Vcosθ and V_y = Vsinθ.

That's how you'd find the x and y components of some vector V, where θ is the angle made with the +x axis.

I'm not sure though that this is where i can put these equations to use, since i don't know the value of V.

According to the diagram, it would be F1.

In looking at the angles, F1 is 60° from the x-axis going counterclockwise.

F1 is 60° below the negative x axis. So will the x-component of F1 be negative or positive?

 

[cdornz]

If the x-component is below the negative x-axis i would think that that component would be negative. But using those equations I think I've determined the answer.

F1x=F1cos60°
F1y=F1sin30°

I broke this down by drawing out the picture of the triangle somewhat given and by finding the f1x and f1y components and plugging those into the equations I had.

 

[Doc Al]

If the x-component is below the negative x-axis i would think that that component would be negative. But using those equations I think I've determined the answer.

F1x=F1cos60°
F1y=F1sin30°

I broke this down by drawing out the picture of the triangle somewhat given and by finding the f1x and f1y components and plugging those into the equations I had.

Looks OK except for the signs.

 

[cdornz]

In question with the signs, would the x-component be negative because it is technically below the F1 and the y-component positive because it is technically above the F1?

 

[Doc Al]

In question with the signs, would the x-component be negative because it is technically below the F1 and the y-component positive because it is technically above the F1?

Hint: Redraw the vector F1 so its tail is at the point of application. Or at least imagine a set of axes with the origin at the tail of F1. That will make it easier to see the signs of the components.

The x-component of F1 is negative since F1 points to the left of the vertical axis.

The y-component of F1 is negative since F1 points below the horizontal axis.