# What is k for the bottom spring?

Tags:
1. Nov 1, 2016

### emily081715

1. The problem statement, all variables and given/known data
A 5.0-kg block suspended from a spring scale is slowly lowered onto a vertical spring.
Part A: What does the scale read before the block touches the vertical spring?
Part B: If the scale reads 32 N when the bottom spring is compressed 30 mm, what is k for the bottom spring?

2. Relevant equations
F=kx

3. The attempt at a solution
K=32/0.03= 1066.7N/m

2. Nov 1, 2016

### BvU

So would 32 N be the force the block exerts on the bottom spring ?

3. Nov 1, 2016

### emily081715

thats what i interpret from the question, is that not correct?

4. Nov 1, 2016

### BvU

If the scale reads 32 N, and $g$ times the mass is 49.1 N ...
Draw a diagram of the forces on the block.

5. Nov 1, 2016

### emily081715

Both forces are acting down so would it be (32+49.)1/0.03=2703

6. Nov 1, 2016

### BvU

The scale is pulling the block up
The bottom spring is pushing the block up
The earth is pulling the block down
Fnet = ma and the block is not accelerating

7. Nov 1, 2016

### emily081715

Would it still not be what I did earlier

8. Nov 1, 2016

No.

9. Nov 1, 2016

### emily081715

why? what is the mistake, should the forces be subtracted

10. Nov 1, 2016

### BvU

Draw the forces the scale and the spring exert. Which way do they point ?