Simple Harmonic Motion: Position, Velocity, & Acceleration

[hardygirl989]

Homework Statement

A 1.00-kg glider attached to a spring with a force constant 49.0 N/m oscillates on a frictionless, horizontal air track. At t = 0, the glider is released from rest at x = -3.50 cm (that is, the spring is compressed by 3.50 cm).

Find the position, velocity, and acceleration as functions of time. (Where position is in m, velocity is in m/s, acceleration is in m/s2, and t is in s. Use the following as necessary: t.)

Homework Equations

x(t)=Acos(ωt+∅)

The Attempt at a Solution

I know that the amplitude is going to be positive 0.035m
Thus, x(t)=0.035cos(ωt+∅)

Also, ω=√(k/m)=√(49/1)=7rad/s
∴ x(t)=0.035cos(7t+∅)

The only thing I am still confused about is how to find ∅...Can anyone help please and thank you?

 

[azizlwl]

Compare with simple Cosine graph y=Cos(θ).
Check what is new function be if it is shifted to the left by certain radian.

 

[hardygirl989]

The phase shift for the cosθ would be ∏
∴ x(t)=0.035cos(7t+∏)

Thank you!

SOLVED.