Determining Momentum and Energy Loss of Balls Colliding Against 
Different Surfaces

Rich, Loretta South Shore High School

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.
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