# Stretched Spring

#### 12boone

1. Homework Statement
A spring with 58 hangs vertically next to a ruler. The end of the spring is next to the 15- mark on the ruler. If a 2.0- mass is now attached to the end of the spring, where will the end of the spring line up with the ruler marks?

2. Homework Equations

I used F=KX should it be mgy=kx? or mgy=1/2kx^2

3. The Attempt at a Solution

My solution was 32 centimeters and 34 centimeters and those were both wrong. Must use two sig figs.

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#### LowlyPion

Homework Helper
1. Homework Statement
A spring with 58 hangs vertically next to a ruler. The end of the spring is next to the 15- mark on the ruler. If a 2.0- mass is now attached to the end of the spring, where will the end of the spring line up with the ruler marks?

2. Homework Equations

I used F=KX should it be mgy=kx? or mgy=1/2kx^2

3. The Attempt at a Solution

My solution was 32 centimeters and 34 centimeters and those were both wrong. Must use two sig figs.
With F=-kx you can know k by the original measurement - assuming that 0 is the 0 force point. This implies that each unit represents 58*g/15 units of force. Adding another 2*g units of force means that you will get an additional 2*g*15/58*g units. This suggest then it will lengthen to 15+(30/58) units.

I'm curious where you got cm out of your description. Or is there a picture you aren't sharing and other units you haven't mentioned?

#### 12boone

oh the ruler was 15 cm

#### 12boone

sorry i guess my copy paste didnt work. The 58 is 58 N/m and is the K and it hangs next to a spring that is next to a ruler at 15 cm. If you add 2 kg to it what is the new measured distance?

#### LowlyPion

Homework Helper
sorry i guess my copy paste didnt work. The 58 is 58 N/m and is the K and it hangs next to a spring that is next to a ruler at 15 cm. If you add 2 kg to it what is the new measured distance?
I still have no idea where the origin is. But 2 kg will move it 2*9.8/58 m.

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