Name three devices or inventions which are designed to decrease friction

The place you get your hair cut has two nearly parallel mirrors 6.00 m apart. as you sit in the chair, your head is 2.00 m from the nearer mirror. looking toward this mirror, you first see your face and then, farther away, the back of your head. (the mirrors need to be slightly nonparallel for you to be able to see the back of your head, but you can treat them as parallel in this problem.) how far away does the back of your head appear to be?

What is the measurement of how fast an object moves relative to a reference point?

If two parallel light rays hit a mirror, they will not be parallel to each other after they reflect.