What Is the Speed of a Mass Displaced from Equilibrium on a Spring?

[nlkush]

Homework Statement

A 0.340kg- mass is attached to a spring with a force constant of 13.0 N/m.
If the mass is displaced 0.250m from equilibrium and released, what is its speed when it is 0.140m from equilibrium?
in m/s
for some reason cannot get the correct answer.

 

[Doc Al]

Show what you did.

 

[nlkush]

omega=square roote of k\m
T=1.47
k=13.0
not sure of amplitude
eqn v=-Aomega*sin(omegat)

 

[nlkush]

answers were like 0.87 m/s 0.5981m/s
1.54m\s
i cannot seem to get it correct

 

[Doc Al]

Why don't you use energy conservation.