Newton’s Car

Purpose: To investigate how increasing the mass of an object affects acceleration

Materials

• 10 x 20 x 2.5 cm wooden block
• 3 3-inch wood screws with round heads
• 12 round pencils or short lengths of same sized dowel
• plastic film canister
• assorted materials for filling canister
• 3 rubber bands
• cotton string
• eye protection
• metric beam balance
• screwdriver
• meter stick
• scissors
• Newton Car Chart

Background

Newton’s Second Law of Motion states that force equals mass times acceleration. In rockets, the force is the action produced by gas expelled from the engines. According to the law, the greater the gas that is expelled and the faster it accelerates out of the engine, the greater the force or thrust.

Adult Prep

• Drive three screws into the block of wood as indicated on diagram 1.
• If using dowels instead of pencils, measure and cut 12 pieces the same length.

Procedure

1. Cut six pieces of string 15 cm in length.
2. Tie each string into a loop making sure that all loops are approximately the same size.
3. Fill the film canister with objects and find the mass in grams. Record the mass in Newton Car Chart.
4. Slip a rubber band through the string loop. See diagram 2.
5. Stretch the rubber band over the two screws and pull the string back over the third screw. See diagram 3.
6. On a flat surface, arrange the rods parallel to each other so that they are 6 cm apart. Place the wooden block (car) on top of three rods. See diagram 4.
7. Put on eye protection.
8. Position yourself so that you are not in the path of the canister when it is released.
9. Using a sharp pair of scissors, snip the string.
10. Use a meter stick to measure the distance that the car traveled and record.
11. Repeat steps 4-10 using two rubber bands.
12. Repeat steps 4-10 using three rubber bands.
13. Refill the canister with different objects, determine its mass, and record.
14. Repeat steps 4-12 with the new mass.
15. Determine a color for each mass and color in the box next to the mass appropriately. Using the color indicated, plot your results.

Newton Car Chart