Make motor run slower
There's various type of AC motor. I assume you are talking about single-phase AC motor. But I'm suggesting not to do anything with it without the help of an experienced person. 

The speed of any AC motor can be changed. The most popular way is the variable frequency driver. Besides you can use Triac. Nowadays, solid-state relay IC has become very popular instead of Triac.

And if you start to work with it, be aware of the heat generated in various IC. 

Watch these youtube videos: VFD , Triac ,Solid-state relay

And you will find all of these in any electrical hardware store. 
Solid-state relay
Triac dimmer
VFD

I'm saying again, don't do these alone. Playing with high voltage has two outputs: 1. Coooool, 2. You are in hospital or dead