Momentum ConservedReturn to Physics Index
Savannah Walker Mason School
4712 Keeler Street
Chicago IL 60623
Objectives: The students will apply two of Newton's Laws of Motion discovering that Momentum is conserved. Materials: Newton's Cradle Carts Planks with skates screwed to the bottom "Crash Dummy Motorcycle" Strategy: NEWTON'S CRADLE--Collision Pull one ball out. Ask "What will happen when I let go?" Let everyone contribute. Then let go. See what actually happens. Do not get into a big discussion at this point! Come back to this at the end. TWO CART COLLISION-- Define Momentum: Mass x Velocity. Have two carts of equal mass collide with each other from opposite directions. Ask "What happened?" Let everyone contribute. (Newton III, and Momentum is Conserved) Then have the two carts collide when one of the carts is the same mass as previously and the other has a third cart stacked on top-a larger mass. Ask "What happens?" Let everyone contribute. (still Newton III, also Newton II, Momentum is Conserved) PLANK WITH ROLLER SKATES ATTACHED-- Have a student walk the plank. Ask "What happened?" (Plank goes the other way.) Let every student contribute. Have students of different weights take turns. Observe any difference this makes. (Newton III, Momentum is Conserved) CRASH DUMMY MOTORCYCLE-- Construct a "Wall" at the end of an inclined plane. Have the motorcycle with the dummy rider crash into the wall. Ask "What happened?" (Newton III, also Newton I, Momentum is Conserved) NEWTON'S CRADLE REVISITED-- Go back to the Newton's Cradle. Again pull out one ball. Let go. Ask "What happened?" and "Why?" Students should be able to discuss the results in terms of Newton's Laws for each ball's collision with the next ball. They should also recognize that Momentum is Conserved in each collision. Now try this with two, three, or even four balls. They should be able to extend their conclusions to these unequal mass collisions.