Physics Question on Springs

[ahmed90]

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"Two people pull on a horizontal spring that is attached to an immovable wall. Then, they detach it from the wall and pull on opposite ends of the horizontal spring. They pull just as hard in each case. In which situation, if either, does the spring stretch more?"

I found this question in a Cutnell Physics textbook. Went to the answers section, and it claims that the spring is stretched more when attached to the wall. I really don't see the logic there, so i'm hoping one of you guys can clarify it for me.

 

[Pons Asinorum]

This type of question is better posed in the MCAT Study Questions forum.

Think of each person as pulling with force F. If they're both on one side, and they pull, they pull with force 2*F. How hard does the wall pull against the spring? Newton's 3rd, right. The wall pulls with 2*F, so the force acting on the spring is 2*F. If there are people on each end, they each pull with a force of F. Newton's 3rd, they each pull with F, and the force acting on the spring is F. Draw two FBD's, it should make more sense.

"Two people pull on a horizontal spring that is attached to an immovable wall. Then, they detach it from the wall and pull on opposite ends of the horizontal spring. They pull just as hard in each case. In which situation, if either, does the spring stretch more?"

I found this question in a Cutnell Physics textbook. Went to the answers section, and it claims that the spring is stretched more when attached to the wall. I really don't see the logic there, so i'm hoping one of you guys can clarify it for me.

 

[ahmed90]

Thanks dude