Friction is what happens when two things rub against each other. In some cases we want to prevent friction so it is easier to move. Machines and engines use grease and oil to reduce friction in order to last longer. Another way to reduce friction is to have the object come into contact with less surface area. In the book, The Sled Race, Freddie and Bert learn that friction can have a big impact on the results of their race with Liza! POs: Download Order Form