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Omareg94

Member

Registered: 2013-04-26

Posts: 13

Statics problem: the inclination angle would be 30 only or 30 and 150

Dears,

Quesion:AB is a uniform rod of length 50cm, and weight 20 newton, acting at its mid-point, rotates easily in a vertical plane about a fixed hinge at its end A.  A couple having moment of magnitude 250 newton.cm acts on the rod in the same vertical plane.  Find the measure of the inclination angle of the rod and the hinge reaction on the rod in the state of equilebrium.

Confusion:I reached to sinθ=1/2 then the confusion here is θ=30 only or 30 and 150 as sin150 also equal 1/2
Waiting your reply

Sincerely,
Omar

Bob

Administrator

Registered: 2010-06-20

Posts: 10,646

Re: Statics problem: the inclination angle would be 30 only or 30 and 150

hi Omar

Welcome to the forum.

I cannot see any reason why you shouldn't have two answers for this.

But, which angle are you calculating?

I would expect an angle of inclination to be with respect to the horizontal, 'a' in my diagram below.

http://www.mathwords.com/a/angle_inclination.htm

That means for equilibrium, moments about A

My diagram shows the second answer with dotted lines.

Hope that helps. 

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Omareg94

Member

Registered: 2013-04-26

Posts: 13

Re: Statics problem: the inclination angle would be 30 only or 30 and 150

Thanks for your quick reply and concern, I am sorry for my late reply!
θ is the angle between the rode and the wall.
I have attached the way I've solved via it.
Thanks I have got it, the only confusion is that my book wrote the answer 30 only.

Sincerely,
Omar

Bob

Administrator

Registered: 2010-06-20

Posts: 10,646

Re: Statics problem: the inclination angle would be 30 only or 30 and 150

If theta is between the rod and the wall then 30 or 150 is good.

Cannot see why 150 has been left out.  ??

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Omareg94

Member

Registered: 2013-04-26

Posts: 13

Re: Statics problem: the inclination angle would be 30 only or 30 and 150

Thabks a lot!
Reattached my solution.

Sincerely,
Omar

Last edited by Omareg94 (2013-05-04 03:15:26)

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Statics problem: the inclination angle would be 30 only or 30 and 150

Well, in both cases the inclination angle is 30 degrees, just in different directions.

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