Shutter speeds

Today I learned about shutter speeds, and how to manipulate it. My chosen subject was cars, for one of the shots i had to pan with the car to let the car remain sharp and streak out the background to do this i had to make the shutter slower, i chose 1/3 of a second with a large f-stop. another image we had to freeze the image by making the shutter speed very fast i choose 800/1 by doing this i let very little light into the image so i had to raise both the ISO and the appiture, unfortionally my Appiture only goes down to F. 3.5 but i managed to get the exposure correct.