OK so I am taking physics and I missed the last class due to bad weather.. and now I'm lost. This is the question

A staging that weighs 140 N supports two
painters, one 210 N and the other 370 N. The
reading in the left scale is Fℓ = 610 N.

What is the reading Fr in the right hand
scale?
Answer in units of N

I don't want just an answer, I want it to be explained too if you can so I can be able to try to solve it.. but in ENGLISH.. im horrible at science:D so maybe a formula or something?

I'd love to help, but I'm confused. What scales are you talking about? Was there an illustration to go along with the question?

Otherwise, I'd just have to blindly guess that the two scales together are supporting the total weight of the two painters and the staging (140 + 210 + 370 = 720N total). Since one scale is apparently supporting 610N of the total weight, the other scale must be supporting the remaining 110N.

http://tinypic.com/r/2i8ufeu/7
That's the image of the illustration... thank youuu

http://i56.tinypic.com/2i8ufeu.png

Quote:

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Originally Posted by nelababii

ok so i am taking physics and i missed the last class due to bad weather..and now im lost. this is the question

A staging that weighs 140 N supports two
painters, one 210 N and the other 370 N. The
reading in the left scale is Fâ„“ = 610 N.

What is the reading Fr in the right hand
scale?
Answer in units of N

i dont want just an answer, i want it to be explained too if you can so i can be able to try to solve it..but in ENGLISH..im horrible at science:D so maybe a formula or something?

---

http://i56.tinypic.com/2i8ufeu.png

Thanks.

This is a classical problem in statics, where everything is in a steady state (as opposed to dynamics where objects move and accelerate). There's really only one major thing to remember with static problems: the sum of all the forces acting on the object(s) is zero. Why? Because if the net force wasn't zero, the object(s) would be accelerating (because of Newton's second law: F=ma. If F is not zero and m is not zero, a would have to be nonzero as well).

So let's add up all of the forces. The staging weighs 140 N, and that force is directed downward, so let's call it -140 N. The same logic applies to the two painters, with forces of -210 N and -370 N. Meanwhile, the rope on the left is pulling upward with a force of +610 N (notice the plus sign since the direction of the force is upward). The only remaining force acting on the group is that of the rope on the right. Now we can just solve for it:

(-140) + (-210) + (-370) + 610 + Fr = 0

-720 + 610 + Fr = 0

Fr = 110 N

By the way, you can also think of this problem in terms of Newton's third law: every action has an equal and opposite reaction. Gravity is pulling down on the painters and the scaffolding with a total force of 720 N. Therefore, there must be an equal and opposite reaction, which is the upward force of the two ropes. If one of them is providing 610 N of upward force, the second rope must be taking care of the remaining 110 N.