Resolving Forces: Solving for Unknowns in Mechanics Problems

[studentxlol]

Homework Statement

I'm struggling with question 6 and 7 on this exercise. I have no idea where to start so basic help would be needed to get me started.

Thanks!

 

[AlchemistK]

In what direction would the normal reaction force by the planes act?
Can you resolve the weight vector to make sure that it balances the normal reaction vector?

 

[jedishrfu]

need diagrams and need you to show your work before we can help.

 

[kai_sikorski]

I don't see any reason not to type up that question, other than if you were including a diagram which you didn't anyway. If you're going to ask people for help you could at least make it as easy to help as possible instead of making us all crane our necks with a sideways photograph...

 

[studentxlol]

need diagrams and need you to show your work before we can help.

Here's a better pic.

For question 6, I need to go about finding the normal contact forces P and Q. How do I do that with the info I know?

 

[AlchemistK]

Try finding the angles between the vectors, then resolve the "2g" vector using trigonometry in such a way that the vectors balance each other out.

 

[studentxlol]

Try finding the angles between the vectors, then resolve the "2g" vector using trigonometry in such a way that the vectors balance each other out.

No idea how to do that,

 

[jedishrfu]

well what is the angle of P relative to the horizontal? 40 degrees plus 90 degrees right?

 

[studentxlol]

well what is the angle of P relative to the horizontal? 40 degrees plus 90 degrees right?

No good. I need full method.

 

[jedishrfu]

No good. I need full method.

sorry we can't give you the answer you have to work it out for yourself. you can show us the work and we'll tell you where you went wrong.

 

[studentxlol]

sorry we can't give you the answer you have to work it out for yourself. you can show us the work and we'll tell you where you went wrong.

resolve horizontally, to get an equation for P in terms of Q, let it be (1).

Now resolve vertically, to get another equation in terms of P and Q. Now substitute (1) in this equation to find Q.

So have now got Q, with this i can easily find P by substituting the value of Q in any of the equation.

And as i said before, i don't know if it is the right way, because i haven't came across such a question before.