Calculating Maximum Speed and Initial Displacement of a Glider on a Spring

[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 isn't right. Can someone please help me?

The Attempt at a Solution

 

[Doc Al]

For the first part I thought to use the formula K1+U1=K2+U2 and i came up with 0=.115v^2-.27...

Double check your calculation for 0.27.

 

[physicsgirlie26]

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

Thanks!