What Is the Velocity of a Mass on a Spring When Displacement Is 3.6 cm?

[DLH112]

Homework Statement

This is a 3 part problem and I've successfully solved the first 2 parts, but I don't know what I did wrong in the third part.

1) mass of 346 g on a spring with constant 26.8 N/m on a horizontal + frictionless surface.
Amplitude is 6.7 cm. In part 1 i found the total energy to be 0.0601526 J. and in part 2 i found the max speed to be 0.58966337 m/s.

part 3 is "What is the magnitude of the velocity of the mass when the displacement is equal to 3.6 cm? answer in m/s"

Homework Equations

E = KE + PE , 1/2KA^2 = 1/2kx^2 + 1/2mv^2

The Attempt at a Solution

using the energy from part 1 as E...
0.0601526 = (0.5)(26.8)(0.036)^2 + (0.5)(0.346)v^2
0.061526 = 0.0185328 + (0.5) (0.346)v^2
0.0416198 = (0.5)(0.346)v^2
0.2405768786 = v^2
0.4904863694 m/s = V ... is apparently wrong

 

[Doc Al]

using the energy from part 1 as E...
0.0601526 = (0.5)(26.8)(0.036)^2 + (0.5)(0.346)v^2
0.061526 = 0.0185328 + (0.5) (0.346)v^2

Double check the highlighted term.

 

[DLH112]

ah thank you. i was accidentally using 28.6 instead of 26.8.