Electrical wiring question?

Use a 3 prong plug, the circular pin is ground this gets the green wire, the black wire (hot) goes to smaller straight pin, and the white neutral) wire goes to the larger straight pin.

Don't use a 2 prong plug and don't put the green wire anywhere but the ground pin

It has to do with which wire is live with respect to ground (black is). You usually use a three prong plug.The wide blade is neutral (white wire connects to silver screw on plug) the narrow blade is the black wire (connects to brass screw), the green ground is the circular pin (green screw). If the motor is double insulated (full plastic or rubber case), you can get away with a two prong plug, wide blade is white wire, narrow blade is hot (black wire). Green ground wire would not be present.