Determining Momentum and Energy Loss of Balls Colliding Against 
Different Surfaces

Rich, Loretta                     South Shore High School
                                  933-8180
                           

Objectives:
                                          
1) to relate types of material used in the construction of balls to the 
purpose for which balls are used in certain sports 

2) to show the difference between one-dimensional elastic and inelastic 
collisions 

3) to calculate momentum of various balls colliding against three 
different surfaces and to compare results with theoretical principles 
of conservation and energy 

4) to record/graph test data to compare momenta of balls

5) to determine if water on a surface affects the conservation of 
energy in balls colliding against a surface 

6) to apply principles of momentum and conservation of energy to the 
development of protective mechanisms existing in motor vehicles 

Vocabulary:

collision                            energy
one-dimensional collision            potential energy
elastic/inelastic collision          kinetic energy
momentum                             velocity
conservation of momentum             acceleration
graphing/variables                   conservation of energy

Materials:

1) various balls (see suggested list below)    4) water
2) laboratory balance                          5) blackboard
3) surfaces (wood, concrete/slate, carpet)     6) meter sticks

Strategy:

     Identify various balls used in playing different sports. 
Demonstrate the two types of collisions: elastic and inelastic. 
     Conduct teacher demonstration of using apparatus to determine 
momentum of a bouncing ball.  Make use of transparency displayed on 
overhead projector showing basic set-up for measuring distance(d) ball 
bounced to a point on the meter stick.  Mass the ball used in the 
demonstration and use the distance recorded to calculate the time and 
the velocity of the bouncing ball.  Record results on a data chart.  
Determine the momentum of the bouncing ball and the potential energy 
lost during the collision. 
     Arrange students in groups of 3-4 and give each group three 
different balls to use for the activity.  Obtain the mass for each ball 
and record data.  Using one ball at a time on each surface, drop a ball 
from a given height (l m) onto a surface and measure the point where 
the ball bounced up to the meter stick.  Use the distance (l m) and the 
acceleration due to gravity (10 m/s) to calculate the time (t) that it 
took for the ball to reach the surface. Use the time calculated to 
determine the velocity of the ball as it dropped to the surface. 
Determine the momentum of the dropped ball by multiplying it's mass by 
the velocity.  Repeat entire process using the remaining balls, 
recording data carefully.  Spread water on each surface and again 
bounce each ball, noting any change in the height (d**) recorded.  
Record final results for all balls on chart on blackboard. 
     Compare data recorded by all groups on the blackboard, noting the 
most elastic and/or inelastic balls.  Discuss reasons why a particular 
ball is used in a sport.  Using a transparency  containing 
representative class data, show comparisons of data collected on the 
overhead projector.  Discuss conservation of momentum and conservation 
of energy as it relates to one-dimensional inelastic collisions. 
     Discuss how water affects inelastic collisions against different 
surfaces. 
     Discuss the use of air bags/seatbelts in motor vehicles as safety 
mechanisms to reduce impact force by increasing impact time during 
collisions. 
       
Suggested balls: clay, putty, rubber, ping pong, super ball, steel,
                    golf, tennis, squash, baseball, Nerf ball (sponge)

Transparencies:  general apparatus, chart with test data from three
                    surfaces to be compared

Hand-outs: Calculation sheet with equations used to find time,
              velocity, momentum, and potential energy.