OK,here is my lesson 6 blog post:

I measured sliding friction force by setting down our surface(course sandpaper) on the table.Then,I

hooked the hook on the Newtons scale to the hook on the wooden block.Then,set the ruler next

to the paper.Pull the newtons scale at a medium speed and the wooden block should follow.Get

to 27 cm and then stop.check the number on the scale.that is the friction force.

                         I learned,about controlled variables,that Most of the time,you can predict what

happens.Examples are,Surface area,Weight of the load,How far you pull it,etc.