# Homework Help: Pulley + spring balance problem.

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1. Feb 11, 2016

1. The problem statement, all variables and given/known data
A light spring passing over a smooth pulley carries a spring balance of mass 1 kg and two weights of masses 1 kg and 2 kg. the reading on the balance will be

2. Relevant equations
3. The attempt at a solution

to my knowledge whatever the tension above the spring balance the reading will not change, it is only affected by the reading below it. Therefore I considered
reading = weight of spring balance + 1N
But I'm not sure whether this is the right approach. Should the mass of spring be considered? Or will there be some sort of acceleration taking place?

Thank you.

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2. Feb 11, 2016

### BvU

Hi,

You want to draw a free body diagram of the spring balance.

Is your 1 N a typo? DId you mean 10 N ?

Suppose the spring balance + 1kg weight hangs from a nail in the wall.
What does the balance reading show ?
What is the force on the nail ?​

3. Feb 12, 2016

It was 10 N ^^
So.. It would look like this: (attachment)
Would that be okay?
Thank you

4. Feb 12, 2016

### BvU

I think I agree.
Just for fun: what would the reading be if the spring balance were turned upside down ?

5. Feb 12, 2016

20N?
I'm not very sure though..

6. Feb 12, 2016

### BvU

I agree - again !
I suppose the only way to be really sure is to do the experiment...

7. Feb 12, 2016