Simple harmonic motion of a machine part

[kaywond]

Homework Statement

A machine part is undergoing SHM with a frequency of of 5hz and amplitude of 1.80cm. How long does it take the part to go from x = 0 to -1.80cm?

Homework Equations

x = Acoswt

The Attempt at a Solution

X is given and convert it to metres 0.018. I need to manipulate answer to get time.
angular velocity is 2pi x 5 = 31.41. It is just an equation manipulation. could someone please show me the technique?

 

[Basic_Physics]

The displacement is the negative of the amplitude.

 

[CWatters]

If the peak amplitude is 1.8cm then asking when the displacement is -1.8 makes it rather easy. No need to even use the sin button on the calculator :-)

Sketch displacement vs time. Mark the points 1.8m and -1.8m. If T is the period (=1/5) at what fraction of T does 1.8cm and -1.8cm occur?

 

[kaywond]

thanks 1/5 equals 0.2. Then divide by 4 and 0.05 is the time in seconds

 

[CWatters]

0.05s is one valid answer but there are two possible valid right answers for this question. I recommend you give both.