THE APP YOU GET MUST HAVE A VARIETY OF SHUTTER SPEEDS AVAILABLE.
LOOK FOR THE DENOMINATOR of shutter speed fractions listed (ex: 250, 125, 60, 30, 15, 8, 4...).
If you are using your iPhone (or other) for your camera this semester, you would probably do yourself a favor by purchasing some sort of "slow shutter" app that would allow you to manipulate the shutter speed on your smartphone.
Here are a couple examples:
There are others available, as well.
Check them out, and give yourself more options for creativity by buying one.
This site (CLICK HERE) might have a shutter app for your phone.
Or this site (CLICK HERE) may have one for you.
Here's one for Android: CLICK HERE.