Experiment Setup

Materials:

• Two carts with grooved tracks (the carts must stay firmly on track without turning)
• Masses to load onto carts (to help keep them on track)
• Two meter sticks attached perpendicularly to carts
• Five pulleys
• Three smart pulleys connected to a Pasco 700 interface (preferred) or two smart pulleys connected to a Pasco or Vernier interface. Note: The Pasco 500 interface and the Vernier ULI only have two connections for digital equipment, which is why the Pasco 700 is needed if three pulleys will be used. Three pulleys will allow you to measure and compare x, y, and resultant motion vectors. Two pulleys will only allow you to measure two of those three.
• Chart paper or other large bulk paper
• Small cardboard box or other light sliding object
• String
• Masses to hang on strings
• Masking tape
• Small block of wood to secure string for resultant vector pulley
• Two small blocks of wood to provide friction.

Description of setup:

	It's important to firmly attach the meter sticks to the carts. I wedged small blocks of scrapwood into the top of the carts and then screwed the meter sticks to the blocks of wood. Place the tracks at right angles and put the carts (with meter sticks attached) on the tracks. The relative motion of the carts will provide motion of the cardboard box as the meter sticks slide over each other. Support the far end of the meter sticks any way you can with some kind of low friction sliding bearing. I used plastic meter sticks with paper clips taped to the underside of the wooden meter sticks. Tape some chart paper to the table below the area where the meter sticks cross. Attach a marker to the cardboard box. A small paper tube in which the marker can slide up and down as it "floats" on the paper is effective.
Shown at right are three of the five pulleys used. The other two pulleys are at the far ends of the two tracks. In my setup, it was convenient to clamp a board to the corner of the table to provide room for the three smart pulleys. Place the pulleys on each end of the tracks and attach strings to each end of the carts which run over the pulleys. Hang masses on the pulleys in front of the carts to provide motive force. Hang small masses on the smart pulleys behind the carts to provide tension. Attach a string between the box and the resultant vector pulley. Important: Underneath the crossed meter sticks is a small block of wood with a screw-eye. The string between the box and the resultant vector pulley passes through this eye, ensuring that the measurement of displacement of the resultant vector is from the origin (and keeping the string on the pulley). The block of wood in front of each cart is there to provide friction to slow the motion of the cart. Vary the friction by placing masses on these blocks or adjusting the masses hanging over the pulleys at the far end o f the cart. The two large masses shown on these blocks are there to hold the carts in place between runs.
	As the carts roll, the box is pushed by the two meter sticks, and its motion is the resultant of the motions of the "x" meter stick and the "y" meter stick. One can very the magnitude and type of motion (constant velocity, accelerating) of the two carts to provide different motions of the box. Toward the lower right is a pretty good view of my arrangement for holding the marker.