Thursday

April 17, 2014

April 17, 2014

Posted by **Janice** on Thursday, June 23, 2011 at 6:28pm.

- Physics -
**Damon**, Thursday, June 23, 2011 at 6:32pmWhen there is no compression OR tension on the spring, usually we call the potential energy zero.

If you either compress it or stretch it, the potential energy increases.

U = (1/2)k x^2

that is + for -x and for +x

The kinetic energy is only when the mass is moving

Ke = (1/2)m v^2

- Physics -
**Janice**, Thursday, June 23, 2011 at 6:37pmSo my results are incorrect right? The PE should not be 0 when compressed.

- Physics -
**bobpursley**, Thursday, June 23, 2011 at 6:44pm - Physics -
**Damon**, Thursday, June 23, 2011 at 6:48pm250 gram = .25 Kg

weight = m g = .25*9.8 = 2.45 Newtons

That stretched the spring 1.42 cm?

1.42 cm = .0142 meters

so k of spring = force/elongation =2.45/.0142 = 172.5 Newtons/meter

Potential energy stored in spring = (1/2)k x^2

=(1/2)(172.5)(.0142)^2 = .0174 Joules

Potential energy lost by mass going down in gravity field = m g h

= .25*9.8*.0142 = .0348 Joules

The mass lost more potential energy than the spring gained (twice as much)

So we have .0174 Joules left over when the mass stretches the spring. That energy goes into kinetic energy. The mass falls through that .0142 down point and keeps going for another .0142 meters where it comes to a stop, then bounces back up again to the start, again and again :)

- Physics -
**Damon**, Thursday, June 23, 2011 at 6:52pmThe nasty thing about potential energy is that you can define zero anywhere at all. What matters are differences.

- Physics -
**Janice**, Thursday, June 23, 2011 at 6:54pmThanks guys info really helped!

**Related Questions**

Physics - So I did in an experiment and the results I got were the potential ...

Physics - Pushing on the pump of a soap dispenser compresses a small spring. ...

physics - Pushing on the pump of a soap dispenser compresses a small spring. ...

physics - Janet wants to find the spring constant of a given spring, so she ...

physics - A spring (spring 1) with a spring constant of 520N/m is attached to a...

physics - a spring with spring constant k= 100N/m is at its equilibrium length a...

Physics ( elestic potential energy) - A spring with a force of 5.2 N/m has a ...

physics - An object of mass M = 4 kg slides from rest a distance d = 2 m down a ...

physics - A spring has a force constant of 410.0 N/m. (a) Determine the ...

science/physics - A spring has a force constant of 590.0 N/m. (a) Determine the ...