# Mechanics Help

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#1
Hi,

I had some trouble with the following question:

How do they get the distances? I get its the perpendicular distance from X, but I don't understand how they worked that out.

Any help is appreciated!
0
3 weeks ago
#2
(Original post by Navboi)
Hi,

I had some trouble with the following question:

How do they get the distances? I get its the perpendicular distance from X, but I don't understand how they worked that out.

Any help is appreciated!
For the first one,
a*cos(theta)
Is the horizontal distance from the bottom left "RF origin" (where the force W is perpendicular). This is the same axis where F is pointing. This is also the same from X by projecting the force W upwards rather than downwards (and again considering the horizontal distance from X where the force is perpendicular).

The others are similar. The ladder is length 2a and you use sin / cos to work out the vertical and horizontal distance from X.
Last edited by mqb2766; 3 weeks ago
1
#3
(Original post by mqb2766)
For the first one,
a*cos(theta)
Is the horizontal distance from the bottom left "RF origin" (where the force W is perpendicular). This is the same axis where F is pointing. This is also the same from X by projecting the force W upwards rather than downwards (and again considering the horizontal distance from X where the force is perpendicular).

The others are similar. The ladder is length 2a and you use sin / cos to work out the vertical and horizontal distance from X.
oh okay, I understand now, thanks!
0
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