Use your bookbag or other heavy object to keep the track from sliding down. The height, in this experiment, should never change. It is always the distance from the floor to the place where the track meets the desk. However, you may choose to measure the length as indicated, or you may use the cm. Keep in mind which length you record, because you will have a different method for calculating your angle of incline.
Procedure Weigh the block of wood, record in newtons.
Clean and smooth the surfaces of the plane and the block to make them as frictionless as possible. Set up the track as described above and determine the angle of incline. Hook a spring scale, or other force measuring device, to the hook on the block and pull it up the plane with a constant velocity. Have your partner read and calculate the value on the spring scale during the pull. The force you applied with the spring scale is the equilibriant of the component of the block's weight parallel to the plane plus the force of friction.