How to Make a Machine in the Classroom That Measures Force
- 1). Orient the clipboard or hardboard with the long sides placed vertically. You do not need to remove the clip portion of the clipboard. Measure 2 ½ inches in from each side of the hardboard along the bottom edge. Mark each point with the pencil. Measure upwards 9 inches on each long side, then measure in toward the center of the hardboard 2 ½ inches. Mark each point with the pencil. Connect the four points to make a rectangle.
- 2). Saw along the marked line on the left side from the bottom edge up. As you approach the marked horizontal line, round the corner slightly and saw along the horizontal line approximately halfway. Repeat the procedure for the marked line on the right side. Remove the rectangle of hardboard. The hardboard will look similar to a wide, inverted "U."
- 3). Measure 4 ½ inches up from the bottom edge of the left leg of the "U" and 1½ inches in from the left side. Mark with the pencil. Repeat the procedure on the right leg. Make a hole through each marked point using the hammer and nail. Insert a brass fastener in each hole. Bend the prongs to hold the fastener in place. Twist the rubber band twice and stretch it over the brass fasteners, hooking it under the fastener head.
- 4). Lay the ruler along the inside edge of the left leg of the hardboard. Draw a horizontal line with the pencil from the center of the nail hole to the inside edge of the leg. From that line, mark with the pencil every ½ inch up and down the left leg. Repeat the procedure on the right leg. Label the line at the nail hole "0." Label the next line up "1" and continue in order. From "0," label the next line down "1" and continue in order. These will be called "units of force." Darken each line with the marker after you are certain you have measured correctly. Alternatively, older students can make calibrated marks using a spring scale. Mark a line with the pencil from the center of the nail hole to the inside edge of the left leg. Label this line "0." Hook the spring scale to the center of the rubber band. Pull on the scale and mark the position of the rubber band with the pencil at various readings of the spring scale using Newtons and/or pounds. Darken each line with the marker after you are certain you have measured correctly.
- 5). Measure the force of your finger pushing against the rubber band. Push harder and note that the units of force will be greater. Hang the S-hook on the rubber band. Tie the string around the can, book or other object you wish to use and hang it on the hook. Measure the units of force for each object.
