# Homework Help: Pulleys and Spring Scales

1. Mar 6, 2013

### mcnealymt

1. The problem statement, all variables and given/known data
The question shows two 5kg masses at rest hanging from two pulleys on opposite ends of a table. The string is massless and the pulley is frictionless.

2. Relevant equations
They want to know what the spring scale reads (in the middle of the masslessstring).

3. The attempt at a solution
This is what I thought:

Fspring= w=mg
5kg*9.8m/s^2= 49N

Would the answer be 98N since both masses are the same?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Mar 6, 2013

### Staff: Mentor

Assuming I understand the setup, the spring scale will read the tension in the string.

I'd say that answer was correct. Why do you think it's wrong?

No.

3. Mar 6, 2013

4. Mar 6, 2013

5. Mar 6, 2013

### mcnealymt

I must be going crazy . What about the mass of the system? Wouldn't it be 10?

Last edited: Mar 6, 2013
6. Mar 6, 2013

### Staff: Mentor

If by "system" you mean both 5 kg masses together, then sure.

What are the exact questions you are being asked?

7. Mar 6, 2013

### mcnealymt

The string is massless and the pulley is frictionless. The spring sclae reads in kg. What is the reading of the scale?

8. Mar 6, 2013

### Staff: Mentor

There's the problem: They want the answer in kg, not Newtons.

9. Mar 6, 2013

### mcnealymt

So wouldn't the answer just be five because 49N is 5kg.

10. Mar 6, 2013

### Staff: Mentor

Yes, the answer will be 5 kg.

11. Mar 6, 2013

### mcnealymt

Thank you Doc Al. I highly appreciate it.