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IAmSparticus

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**1. A 0.69 kg block is hung from and stretches a spring that is attached to the ceiling. A second block is attached to the first one, and the amount that the spring stretches from its unstrained length increases by a factor of 5. What is the mass of the second block?**

**2. Force= spring constant*displacement of spring from unstrained length**

3. First off, I'm horrible at algebra so sorry if I make stupid mistakes in this attempt. The force is gravity so that becomes mg (.69kg*9.8 m/s/s).

mg=kx

If I pick a spring constant of 10 (does it matter what I pick?) then the equation becomes:

(.69kg)(9.8m/s/s)=10 x

Which would give a displacement of .6762 m. Now, when we increase it by a factor of 5, that displacement becomes 3.381 m. Plugging that into a new equations gives:

m (9.8m/s/s) = 10 (3.381m)

When I solve for m I get 3.45 kg, which is wrong. Someone tell me what I did wrong?