Stack 4 to 6 thick books on the floor. Make sure the floor is empty and clean.
Fold a game board and rest one end on the stack of books. Make the other end of the board touch the floor.
Tape the edge of the board to the topmost book. Use a light cellophane tape and a hard-bound book so the tape will damage neither the game board nor the book. Your inclined plane is ready.
Place a light ball such as a ping-pong (or table tennis) ball, tennis ball or a golf ball at the extreme high end of the inclined plane (or the end of the game board touching the books). Release the ball gently and let it roll off the plane onto the floor. Do the same with toy cars.
Make holes in the center of four paper plates using a sharp-pointed pencil. Do not make the holes any bigger than the diameter of the pencil.
Place two of the paper plates next to each other. Apply glue on about one centimeter thick border of the plate surfaces that faces upwards.
Place one plate upside down on each of the two plates so that the top and bottom plates are exactly aligned with each other. Press the sides to make the top and bottom plate stick together firmly. You have made two wheels.
Pick up the first wheel and pass the pencil through the holes which should be aligned. Leave half inch of the pencil on one side of the wheel, pulling the rest of the pencil through the holes. Pass the other end through the second wheel leaving half an inch on the outer side. Your simple machine is ready. Try rolling the wheels on a smooth surface holding the two ends of the axle (the pencil). Twirl the axle with your fingers if needed.
Cut a strip of sharp-edged printer paper three inches wide and 10 inches long.
Mark a point two inches down one short end of the strip. Draw a slanted line starting at two inches from the other end and ending at the point marked on the first end. Cut along this line so that one end is only two inches thick instead of three.
Cut a rectangular slit in the broad end large enough for two fingers to slide in. This simple machine is a wedge.
Wrap a sheet of thin plastic wrap very tightly on a large bowl to cover the bowl. Try cutting the plastic wrap with your wedge using a back-and-forth, sawing motion.