Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Omareg94****Member**- Registered: 2013-04-26
- Posts: 13

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

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,452

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

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 Bundy

Offline

**Omareg94****Member**- Registered: 2013-04-26
- Posts: 13

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

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,452

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 Bundy

Offline

**Omareg94****Member**- Registered: 2013-04-26
- Posts: 13

Thabks a lot!

Reattached my solution.

Sincerely,

Omar

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

Offline

**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,039

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

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline