Forces in balance

  • #1
Hi all,

I am an architect student in college and I am trying to calculate the reactions in the question in the follwing url ( https://www.flickr.com/photos/[email protected]/16250310830/ ) I have attempted the question and got two values which can be seen in the following url (https://www.flickr.com/photos/[email protected]/16251461949/ ) . What I don't understand though is how to calculate whether the reaction is clockwise or anticlockwise thus assigning it a positive or negative value if anyone could tell how to do this and whether my answers are correct it would be greatly appreciated!

Many thanks,
Clockworkrobot
 

Answers and Replies

  • #2
haruspex
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Hi all,

I am an architect student in college and I am trying to calculate the reactions in the question in the follwing url ( https://www.flickr.com/photos/[email protected]/16250310830/ ) I have attempted the question and got two values which can be seen in the following url (https://www.flickr.com/photos/[email protected]/16251461949/ ) . What I don't understand though is how to calculate whether the reaction is clockwise or anticlockwise thus assigning it a positive or negative value if anyone could tell how to do this and whether my answers are correct it would be greatly appreciated!

Many thanks,
Clockworkrobot
The reactions are forces, not torques, so there is no question of clockwise or anticlockwise for those.
To deduce them, you wrote a torque equation. In the way you've written it, you've taken the reactions as positive upwards, but the loads as positive downwards. That required you to reverse the signs.
A purist might have written the equation so that all forces are positive upwards and all torques positive anticlockwise, giving
RL*0 + (-25)*0.4 + (-10)*0.6 + RR*1.2 = 0.
 

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