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Momentum and the Physics of a Slapshot

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  Document Type: Lesson Plan
  Lesson Plan Type: Video,Interactive Instruction
  Subject: Science
  Grade Level: 6,7,8
  Time: 60 minute period
  Last Updated: 02-11-2010
     
  Keywords:
     
     
 
Created/Provided by:
NBC Learn
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CALIFORNIA STATE STANDARDS ADDRESSED

Science/8/Focus on Physical Science
1.0 The velocity of an object is the rate of change of its position. As a basis for understanding this concept: a. Students know position is defined in relation to some choice of a standard reference point and a set of reference directions. b. Students know that average speed is the total distance traveled divided by the total time elapsed and that the speed of an object along the path traveled can vary. c. Students know how to solve problems involving distance, time, and average speed. d. Students know the velocity of an object must be described by specifying both the direction and the speed of the object. e. Students know changes in velocity may be due to changes in speed, direction, or both. f. Students know how to interpret graphs of position versus time and graphs of speed versus time for motion in a single direction.
2.0 Unbalanced forces cause changes in velocity. As a basis for understanding this concept: a. Students know a force has both direction and magnitude. b. Students know when an object is subject to two or more forces at once, the result is the cumulative effect of all the forces. c. Students know when the forces on an object are balanced, the motion of the object does not change. d. Students know how to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction. e. Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction). f. Students know the greater the mass of an object, the more force is needed to achieve the same rate of change in motion. g. Students know the role of gravity in forming and maintaining the shapes of planets, stars, and the solar system.
 
BRIEF DESCRIPTION
Students will begin this lesson by investigating a fun and memorable elastic collision. After watching the NBC Learn Video, Slapshot Physics: Hockey, they will use dynamics carts (or skateboards) to investigate and develop a conceptual understanding of the conservation of momentum.

 

 
PROCEDURES
 
Goal(s):
Students will learn from an investigation that momentum is conserved when two objects collide. They will learn that kinetic energy is conserved in an elastic collision, but not conserved in an inelastic collision. Students will learn how a hockey player uses the laws of physics to create a 90 mile per hour slap shot.
 
Specific Objectives:
Students will be able to:
  1. Explain with words or with an equation that the momentum of an object depends upon both the mass and velocity of the object.
  2. Explain that in a collision between 2 objects that the momentum of the system is conserved.
  3. Describe, qualitatively, the difference between an elastic collision and an inelastic collisions, and give examples of each.
  4. Describe how the conservation of momentum applies to the hockey slap shot.
 
Required Materials:
For introduction demonstration:
Any small bouncy ball and a larger bouncy ball, for example a tennis ball/soccer ball, racquet ball/basketball, ping pong ball/tennis ball, etc.

For the conservation of momentum activity (per group):
2 dynamics designed for collision investigations (as shown in figure 1 below), and weights sets (if dynamics carts are not available, you can ask students to bring skateboards and also use telephone books or other comparable weight)

Optional: hockey stick, piece of clay
 
Anticipatory Set (Lead-in):
Ask students “if you had to choose between being hit by a baseball traveling at 50 miles per hour or a ping pong ball at the same speed, which would they choose and why?” and see if you can work them toward the concept that mass is very relevant in this decision. Next ask them “what if you had to choose between tennis ball traveling at 1 mile per hour and a ping pong ball traveling at 300 miles per hour?” Use this question to clarify that in a collision, it is important to consider both the mass and the velocity of the object, and have them fill in the first 2 answers on the worksheet (defining momentum in words and as an equation, momentum = mass x velocity.)
 
Lesson Plan Procedure:
Note: This lesson assumes prior knowledge of kinetic energy.

  1. Do a short fun demonstration of an elastic collision (see figures 2 and 3 below). Place a small bouncy ball on top of the larger one and drop to the ground. (Caution, the smaller ball will go shooting off at a very high speed so you should practice and use safety goggles if using a particularly small ball.) Briefly discuss that in addition to momentum, we also see that the smaller object gains kinetic energy.
  2. Drop a piece of clay to demonstrate and inelastic collision and discuss that in an elastic collision, kinetic energy is conserved, while in an inelastic collision, it is not.
  3. Have students answer worksheet question 3, describing the difference between an elastic collision and an inelastic collision.
  4. Before watching the video, you can mention that in addition to concepts of momentum there are some other very interesting things presented in the video:  (a) The speed of a slap shot (nearly 100 mph).  (b) Athletes can also be academics (Julie Chu is a 2 time Olympic medalist and a graduate from Harvard).  (c) High speed cameras can take up to 1500 pictures per second.  (d) There is much more physics and technique to a good slap shot than most people realize (hitting the ice first, flexing of the stick, kinetic energy, follow through, gyroscopic effect, etc.).  (e) If you have a hockey stick, you might want to show it and demonstrate that it does not easily flex.
  5. Show the NBC Learn Video: Slap Shot Physics: Hockey
  6. Now have them work in groups to investigate the transfer of momentum during a collision. Instruct them as follows and ask them to record their observations on the activity sheet. (a) Explain to the students that during these collisions, they should investigate what happens when a moving object collides with a stationary object (as is sometimes, but not always, the case with slap shots). (b) Begin by having the carts the same weight. (c) They should observe carefully the situation just before and just after the collision and describe them with words and pictures. (d) As time permits, they should try other variations with unequal masses.
  7. Stop the activity with enough time for them to clean up and as a class go over the final reflection. ( For this final discussion note that the conservation of momentum only applies to systems with no external net forces. Frictional effects will lead to some loss of momentum from the system. If the discussion and observations are restricted to just before and just after the collisions, the class should come to the consensus that momentum is definitely transferred and generally conserved.)
graphics
 
Closure (Reflect Anticipatory Set):
Remind them that elastic and inelastic collisions occur throughout their day and they will have a chance for homework to identify some of them.
 
Assessments & notes
 
Plan for Independent Practice:
For homework have them list some examples of collisions they have seen in their lives. For each collision, students should identify and explain whether they were elastic or inelastic.
 
Assessment Based on Objectives:
Quiz: Conservation of Momentum and the Physics of a Slap Shot
 
Possible Connections to Other Subjects:
Art: Drawing before and after pictures of collisions is a very helpful technique for setting up quantitative momentum problems. Students can draw more elaborate pictures to show the momentum of system components before and after collisions.
 
Adaptations & Extensions:
Use video analysis or an online physics simulation to quantitatively demonstrate the conservation of momentum.
 
 
 
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Submitted by NBCLearn on Tue, 01/26/2010 - 04:14


Title:

Momentum and the Physics of a Slapshot

Grade Level:

6,7,8

Subject:

Science

Author:

nbclearn

Time:

60 minute period

Lesson Plan Type:

Video,Interactive Instruction

Keywords:

Slapshot, Elastic Collision, Inelastic Collision, Momentum, Conservation of Energy, Kinetic Energy, Olympics

Brief Description:

Students will begin this lesson by investigating a fun and memorable elastic collision. After watching the NBC Learn Video, Slapshot Physics: Hockey, they will use dynamics carts (or skateboards) to investigate and develop a conceptual understanding of the conservation of momentum.

 


California State Standards Addressed:

Science/8/Focus on Physical Science)1.0,2.0

Related Links:

Link 1:

Goal(s):

Students will learn from an investigation that momentum is conserved when two objects collide. They will learn that kinetic energy is conserved in an elastic collision, but not conserved in an inelastic collision. Students will learn how a hockey player uses the laws of physics to create a 90 mile per hour slap shot.

Specific Objectives:

Students will be able to:
  1. Explain with words or with an equation that the momentum of an object depends upon both the mass and velocity of the object.
  2. Explain that in a collision between 2 objects that the momentum of the system is conserved.
  3. Describe, qualitatively, the difference between an elastic collision and an inelastic collisions, and give examples of each.
  4. Describe how the conservation of momentum applies to the hockey slap shot.

Required Materials:

For introduction demonstration:
Any small bouncy ball and a larger bouncy ball, for example a tennis ball/soccer ball, racquet ball/basketball, ping pong ball/tennis ball, etc.

For the conservation of momentum activity (per group):
2 dynamics designed for collision investigations (as shown in figure 1 below), and weights sets (if dynamics carts are not available, you can ask students to bring skateboards and also use telephone books or other comparable weight)

Optional: hockey stick, piece of clay


Anticipatory Set (Lead-in):

Ask students “if you had to choose between being hit by a baseball traveling at 50 miles per hour or a ping pong ball at the same speed, which would they choose and why?” and see if you can work them toward the concept that mass is very relevant in this decision. Next ask them “what if you had to choose between tennis ball traveling at 1 mile per hour and a ping pong ball traveling at 300 miles per hour?” Use this question to clarify that in a collision, it is important to consider both the mass and the velocity of the object, and have them fill in the first 2 answers on the worksheet (defining momentum in words and as an equation, momentum = mass x velocity.)

Lesson Plan Procedure:

Note: This lesson assumes prior knowledge of kinetic energy.

  1. Do a short fun demonstration of an elastic collision (see figures 2 and 3 below). Place a small bouncy ball on top of the larger one and drop to the ground. (Caution, the smaller ball will go shooting off at a very high speed so you should practice and use safety goggles if using a particularly small ball.) Briefly discuss that in addition to momentum, we also see that the smaller object gains kinetic energy.
  2. Drop a piece of clay to demonstrate and inelastic collision and discuss that in an elastic collision, kinetic energy is conserved, while in an inelastic collision, it is not.
  3. Have students answer worksheet question 3, describing the difference between an elastic collision and an inelastic collision.
  4. Before watching the video, you can mention that in addition to concepts of momentum there are some other very interesting things presented in the video:  (a) The speed of a slap shot (nearly 100 mph).  (b) Athletes can also be academics (Julie Chu is a 2 time Olympic medalist and a graduate from Harvard).  (c) High speed cameras can take up to 1500 pictures per second.  (d) There is much more physics and technique to a good slap shot than most people realize (hitting the ice first, flexing of the stick, kinetic energy, follow through, gyroscopic effect, etc.).  (e) If you have a hockey stick, you might want to show it and demonstrate that it does not easily flex.
  5. Show the NBC Learn Video: Slap Shot Physics: Hockey
  6. Now have them work in groups to investigate the transfer of momentum during a collision. Instruct them as follows and ask them to record their observations on the activity sheet. (a) Explain to the students that during these collisions, they should investigate what happens when a moving object collides with a stationary object (as is sometimes, but not always, the case with slap shots). (b) Begin by having the carts the same weight. (c) They should observe carefully the situation just before and just after the collision and describe them with words and pictures. (d) As time permits, they should try other variations with unequal masses.
  7. Stop the activity with enough time for them to clean up and as a class go over the final reflection. ( For this final discussion note that the conservation of momentum only applies to systems with no external net forces. Frictional effects will lead to some loss of momentum from the system. If the discussion and observations are restricted to just before and just after the collisions, the class should come to the consensus that momentum is definitely transferred and generally conserved.)
graphics

Closure (Reflect Anticipatory Set):

Remind them that elastic and inelastic collisions occur throughout their day and they will have a chance for homework to identify some of them.

Plan for Independent Practice:

For homework have them list some examples of collisions they have seen in their lives. For each collision, students should identify and explain whether they were elastic or inelastic.

Assessment Based on Objectives:

Quiz: Conservation of Momentum and the Physics of a Slap Shot

Possible Connections to Other Subjects:

Art: Drawing before and after pictures of collisions is a very helpful technique for setting up quantitative momentum problems. Students can draw more elaborate pictures to show the momentum of system components before and after collisions.

Adaptations and Extensions:

Use video analysis or an online physics simulation to quantitatively demonstrate the conservation of momentum.

Additional Notes:




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