# Speed and displacement. please help!

1. Oct 14, 2007

### physicsgirlie26

A glider with mass m= 0.230 kg sits on a frictionless horizontal air track, connected to a spring with force constant k= 5.40 N/m. You pull on the glider, stretching the spring 0.100 m, and then release it with no initial velocity. The glider begins to move back toward its equilibrium position (x=0).

What is the speed of the glider when it returns to ?

What must the initial displacement of the glider be if its maximum speed in the subsequent motion is to be 2.10 ?

For the first part I thought to use the formula K1+U1=K2+U2 and i came up with 0=.115v^2-.27 and found v = 1.53 m/s but that isnt right. Can someone please help me?

3. The attempt at a solution

2. Oct 14, 2007

### Staff: Mentor

Double check your calculation for 0.27.

3. Oct 14, 2007

### physicsgirlie26

hahaha thanks. no wonder why i got it wrong. Such a silly mistake.

Thanks!

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