Quick question about elastic potential energy?

[sameeralord]

http://www.physicsclassroom.com/class/energy/u5l1b7.gif

Now when the spring recoils, it loses its elastic potential energy to the dart. If it loses its energy how does it come back to its original shape. I'm thinking it is the elastic potential energy that is used to make the coil come back to its orginal shape. Also let's say a spring was compressed and I took my hand away. Now it recoiled back to its shape. The spring didn't transfer any of its added elastic potential energy, to any other object. So does the spring has more energy now.

When I compress a spring I'm thinking I'm adding extra potential energy. Am I adding extra energy or, changing the allready existing energy in the spring to elastic potential energy.

Please excuse anyof my misunderstandings.

Thank you

[tiny-tim]

Hi sameeralord! :smile:
When I compress a spring I'm thinking I'm adding extra potential energy. Am I adding extra energy or, changing the allready existing energy in the spring to elastic potential energy.

When you compress a spring, your finger moves as the spring gets shorter, so the force from your finger does work on the spring.

That work done equals the extra PE (and, yes, it is extra: you added it). :smile:
… Also let's say a spring was compressed and I took my hand away. Now it recoiled back to its shape. The spring didn't transfer any of its added elastic potential energy, to any other object. So does the spring has more energy now.

When you remove your finger, if energy is conserved, the spring will bounce to and fro indefinitely, continually exchanging PE for its own KE (and vice versa).

However, most springs are "damped", and lose energy quite fast. :wink: