- #1

cestlavie

- 10

- 3

- Homework Statement
- What is the spring constant k for the spring shown below? (Diagram attached below, and answers are in N/cm)

- Relevant Equations
- ##F = kx##

$$F=kx$$

$$k=\frac F x= \frac {50+50~N} {5+5~ cm}= \frac {100~N} {10~cm}= 10~N/{cm}$$

However, the answer is ##5~N/cm##, because the force on the spring is ##50~N##. I am having trouble understanding why the force isn't ##50~N## + ##50~N##. The diagram looks as though the spring is experiencing force on both sides, so shouldn't it be the sum of both? The only explanation I am given is to imagine the spring is positioned vertically and a ##50~N## weight is applied to it. Therefore, the floor will apply ##50~N## upward, making ##F=50~N##. But I still see this scenario as having ##100~N## of force. Why isn't the weight accounted for in the equation?