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# M2 Statics - Direction Problems Watch

1. http://www.edexcel.com/migrationdocu...e_20090522.pdf

Question 4)B). I have worked out the horizontal and vertical reactions at the hinge correctly. Horizontal (to the left) as 44.1N, vertical (downwards) as 14.7N. Worked out the magnitude correctly. But I just can't work out the direction. I did arctan(14.7/44.1) = 18.4 degrees, that's the clockwise angle from the downwards vertical (AC). So I added 90, to make 108.4 degrees, and that's the clockwise angle from AB or AD. However, that's not the same as in the markscheme which has the following:

18.4 (0.322 radians) below the line of BA
161.6 (2.82 radians) below the line of AB
(108.4 or 1.89 radians to upward vertical)

Please tell me what I've done wrong ><.
2. Bump
3. Bumpety bump? :<
4. You've got the horizontal reaction in the wrong direction. It's going to the right not the left. The wall AC will be pushing against the rod, if the reaction was to the left (as you say) it wouldn't be in equilibrium.
5. (Original post by Noble.)
You've got the horizontal reaction in the wrong direction. It's going to the right not the left. The wall AC will be pushing against the rod, if the reaction was to the left (as you say) it wouldn't be in equilibrium.
Hmm, just to make sure, the thrust on the diagonal line thing is going diagonally up?
6. (Original post by ViralRiver)
Hmm, just to make sure, the thrust on the diagonal line thing is going diagonally up?
Yeah, because the rod is pushing down on it (weight).
7. (Original post by Noble.)
Yeah, because the rod is pushing down on it (weight).
That means it has a horizontal component ( --> direction). Meaning their must be something in the other direction (<--) for it to be in equilibrium. The hinge reaction at A is the only thing I could see?

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