Stack three of the textbooks atop each other. Lay the plank so that one end is on top of the textbook stack, and the other is on a level surface, such as a table or floor.
Tie a piece of string vertically around the fourth textbook. Lay the textbook on the base of the plank ramp.
Attach the spring scale to the textbook by inserting the hook around the string. Grasp the other end of the scale and pull the textbook up the ramp. Make note of the amount of force (measured in newtons) needed to pull the book up the ramp.
Remove one textbook from the stack and again use the spring scale to pull the tied textbook up the ramp. Determine the amount of force required to pull the book.
Remove another textbook and pull the book up the inclined plane again. Determine the amount of force needed to pull the book.
Remove the last textbook so that the plank is now level. Pull the book across the length of the plank. Determine the amount of force needed to pull the book.
Use a ruler to draw a baseline of 10 inches on a piece of paper.
Lay a pencil on the paper at a right angle to the baseline on the right-hand side. Draw a straight line equal to the length of the pencil.
With the red marker or crayon, use the ruler to draw a third line from the end points of the first two lines that were drawn. Cut out the resulting triangular shape.
Use a piece of tape to attach the vertical edge of the triangle to the pencil so that the triangle looks like a pennant. While holding the left point of the triangle with your left hand, use your right hand to twirl the pencil counter-clockwise to wrap the triangular paper around the pencil.
Secure the end with piece of tape. The red sloping line should be visible winding up the length of the pencil. This should resemble a screw.