The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

M1 Urgent help needed

Moments is perpendicular distance but why is it in that q that the 3gcos30 isn't perpendicular?

Thanks
25e3c1977b15b46cb3e073a0c0b2b518.png40.4KB
886d7838fbeca9de7c8274490fd277de.png21.3KB
Original post by Trihawk7
Moments is perpendicular distance but why is it in that q that the 3gcos30 isn't perpendicular?

Thanks


You want the length of either line in green - see attached. sin60 is the more obvious choice, but cos30 works out the same.

886d7838fbeca9de7c8274490fd277de.png
Reply 2
Avatar for Trihawk7
Trihawk7
OP
21
Original post by ghostwalker
You want the length of either line in green - see attached. sin60 is the more obvious choice, but cos30 works out the same.

886d7838fbeca9de7c8274490fd277de.png


But that isn't part of the 3g is it not?
Original post by Trihawk7
But that isn't part of the 3g is it not?


It's the line of action of the force that you're interested in, and this extends to infinity in both directions.
Reply 4
Avatar for Trihawk7
Trihawk7
OP
21
Original post by ghostwalker
It's the line of action of the force that you're interested in, and this extends to infinity in both directions.


I'm still confused because if you're using the line of action then the 3g isn't connected to it? sorry for being stupid
Original post by Trihawk7
I'm still confused because if you're using the line of action then the 3g isn't connected to it? sorry for being stupid


Not sure what you mean by the 3g isn't connected to the line of action.

The line of action is simply the line along which the force acts.
Reply 6
Avatar for Trihawk7
Trihawk7
OP
21
Original post by ghostwalker
Not sure what you mean by the 3g isn't connected to the line of action.

The line of action is simply the line along which the force acts.


How'd they get 3gcos30 then? sorry
Original post by Trihawk7
How'd they get 3gcos30 then? sorry


The perpendicular distance of the line of action is the green line in my previous diagram which is 1 x sin 60, hence a moment of 3gsin60 refering to the lower triangle.

They seem to have used the other angle in the triangle i.e. 30 degrees, in which case it's cos30 giving 3gcos30.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you