Max Acceleration of Oscillating Platform

[mbrmbrg]

Homework Statement

What is the maximum acceleration of a platform that oscillates with an amplitude of 2.70 cm and at a frequency of 6.40 Hz?

Homework Equations

$$a(t)=-\omega^2x_m\cos{(\omega t=\phi)}$$

$$\omega=2\pi f$$

The Attempt at a Solution

a(t) will be maximized when a'(t)=0 (or when cosine's argument=1; it works out exactly the same).

So I want $$\omega t +\phi=0 or \pi$$. I can shove in (2)(pi)(f) for omega no problem, but I'm stuck with the flipping phase constant. Can I just assume that it's zero??

 

[Saketh]

Why do you care about what's in the cosine? Just set the cosine equal to one - you know that's the maximum value of the cosine function - and plug into the remaining parts of your acceleration expression.

So you would just need to know that $$a_{\mathrm{max}}=\omega^2x_m$$ (Note that the cosine is gone because we set it to unity).

 

[mbrmbrg]

right... thenks.
Finals approach and my brain is fried lalalalalalala.Yes, there is a cause-and-effect going on here, although I am not telepathetic (but I do have dark hair...) AAAACK!