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I have a few questions i need some help on.

1. The problem statement, all variables and given/known data

The position of a particle is given by the expression [tex]x=(4.00m) cos(3.00\pit+\pi)[/tex], where x is in meters and t in seconds. Determine (a) the frequency and period of the motion.

2. Relevant equations

[tex]f=\frac{1}{T}[/tex]

[tex]T=\frac{2\pi}{\omega}[/tex]

3. The attempt at a solution

i got:

[tex]T=\frac{2\pi}{\omega}[/tex]

[tex]T=\frac{2\pi}{3\pi}[/tex]

[tex]T=6.58s[/tex]

[tex]f=\frac{1}{6.5797}[/tex]

[tex]f=0.15Hz[/tex]

This is incorrect according to book's answer, what is wrong???

1. The problem statement, all variables and given/known data

A 0.500kg object attached to a spring with a force constant of 8.00N/m vibrates in simple harmonic motion with an amplitude of 10.0cm. Calculate time it takes the object to move from x=+8.0cm (just after it is released at x=+10cm) to x=0.

3. The attempt at a solution

i tried to use this formula: [tex]x=Acos(kt+\theta)[/tex], however i cannot find t because there is two unknowns.

Instead what should i use?

P.S

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# Vibrations and Wave Question

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