# This problem is driving me crazy!

1. Feb 25, 2007

1. The problem statement, all variables and given/known data
A spring with a pointer attached is hanging next to a scale marked in millimeters. Three different weights (weights A, B and C) are hung from the spring, in turn, as shown below. Weight A weighs 111 N and B weighs 199 N.

there are three pictures of spring scales with weights attached: the first spring with weight A attached is at 40mm the second (with weight B) is at 60mm and the third (with weight C) is at 30mm

(1) Which mark on the scale will the pointer indicate when no package is hung from the spring?
(2) What is the weight of package C?

3. The attempt at a solution
right now i'm just thinking about part 1 so i found the difference in mm and N between A and B so i found 20mm and 88N and i'm pretty sure this is relevant, but i'm really confused and don't know where to go from here!!

2. Feb 25, 2007

### Mindscrape

The first part is basically just asking you to figure out the equilibrium point of the spring. When the mass is hanging from the spring, what keeps the mass from just falling to the floor? Just what does hooke's law say?

3. Feb 25, 2007

so F=kx
88=k20
so the answer would be 4.4?

4. Feb 25, 2007

### Mindscrape

Hooke's law says that the force is proportional to the spring constant and the displacement.

$$F = -k \Delta x$$

5. Feb 25, 2007