Equilibrium - Calculate forces

[Naldo6]

Here is the picture of the Problem in the atachments ok... i need to calculate F1 and F2.

Any suggestions please... i don't know how to begin the exercise. ok help please

 

[tiny-tim]

Here is the picture of the Problem in the atachments ok... i need to calculate F1 and F2.

Hi Naldo6!

In problems like this, you can take components in a direction, or you can take moments about a point.

Try moments!

 

[Naldo6]

how i try that?...

 

[tiny-tim]

moments of forces

how i try that?...

Moments are like a see-saw … the smaller you are, the further away you have to be to balance someone bigger.

In equilibrium, the moments all add up to zero (just like ordinary components of force).

The moment of a force about a point is the force times the distance from that point.

Just choose a point, and calculate all the moments.

 

[Naldo6]

is this correct for F2:

0=-F3D1 - (D1+D2)F4 - (D1+D2+D3)F5 + (D1+D2+D3+D4)F2 - ((D1+D2+D3+D4)/2)(9.8)

then F2= [ F3D1 + (D1+D2)F4 + (D1+D2+D3)F5 + ((D1+D2+D3+D4)/2)(9.8) ] / (D1+D2+D3+D4)

right?...

and then F2 + F3 + F4 + (9.8)(mass) = F1 + F2 to calculate the other righ?...

i do that but i don't get my answers...

 

[tiny-tim]

then F2= [ F3D1 + (D1+D2)F4 + (D1+D2+D3)F5 + ((D1+D2+D3+D4)/2)(9.8) ] / (D1+D2+D3+D4)

Hi Naldo6!

Did you mean to type

F2= [ F3D1 + (D1+D2)F4 + (D1+D2+D3)F5 + ((D1+D2+D3+D4)/2)(9.8)(mass) ] / (D1+D2+D3+D4)?

(which you could simplify to F2= (9.8)(mass)/2 + [ F3D1 + (D1+D2)F4 + (D1+D2+D3)F5] / (D1+D2+D3+D4))

If so, that should be right.

Do D1 etc have numbers?

If so, show us the full calculation, and maybe we can see the mistake.

 

[Naldo6]

ty... i get the correct answer with my formula, i just wa smissing my mass in the F of gravity ... ty a lot