Simple Harmonic Oscillation Problem

[GarrettB]

Homework Statement

The velocity of an object in simple harmonic motion is given by v(t)= -(4.04m/s)sin(21.0t + 1.00π), where t is in seconds. What is the first time after t=0.00 s at which the velocity is -0.149m/s?

Homework Equations

N/A

The Attempt at a Solution

I thought this was an easy question but there must be a flaw somewhere in my logic. I've tried -0.149=-4.04*sin(21t+pi). However, solving for t gives me a negative number. I've also tried doing using cos instead of sin to get rid of the phase constant, but still the wrong answer. It's given me aprrox. 0.07s. Any help would be appreciated

 

[barryj]

A couple of suggestions.
If you change the argument of sin by 2Pi what happens.
You might also use a graphing calculator to plot the function to get some insight as to what is going on.

 

[GarrettB]

Nothing happens if you change it by 2Pi? Since that's one full cycle. But this is 1pi?

 

[barryj]

You probably found the sin^-1 of .149/4.04 and that gave you a negative t. Could you change the 1pi to -p1 and resolve?

 

[GarrettB]

Of course you can, because its a cycle. Appreciate the insight.