Momentum Conserved          

Savannah Walker               Mason School
2510 E. 83rd Street           4712 Keeler Street
Chicago IL 60617              Chicago IL 60623
(312) 374-5342                (312) 534-1530

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.