SHM - mass-spring system on frictionless horizontal surface

[trusean]

Homework Statement

A 250 g block is resting on a frictionless horizontal surface. The block is attached to a
spring. The mass-spring system is compressed by a 2.5 N force and then released from
rest.
(a) The resulting oscillation has a 1.0 s period. What is the spring constant?
(b) What is the amplitude of the oscillation?
(c) How fast is the block moving when it is 30.0 cm from its starting point?
(d) How long does the block take to travel this distance?

Homework Equations

T=2Pi/omega
T=2Pi*sqroot(m/k)
E=1/2mv^2 + 1/2kx^2=1/2kA^2
v=omega*sqroot(A^2-x^2)
m=mass
k=spring constant
A=amplitude

The Attempt at a Solution

I have solved for a) the spring constant, 9.87N/m. Then I tryed to use Fs=2.5N to solve for the A by applying the equation F=-kx, where x would repersent the amplitude. This is not working out because my A=0.25m and when inputed into equation for velocity, I get a negitive value under the square root, not allowed. So I was wondering if anyone had some input on this problem. Thank you.

 

[Doc Al]

Realize that the starting point is not the equilibrium point. 30 cm from the starting point will bring you how far from equilibrium?

 

[trusean]

Sorry it took so long to answer. Having the amplitude equal 25cm, I am thinking it is located 25cm from the equilibrium, and thus 30cm from the starting point would be 5cm from the equilibrium?

 

[Doc Al]

You got it!

 

[trusean]

cool, thank you very much for your help, have a good one. And by the way, I just found this forum and I think this is a great tool for students, keep it up. peace