## SCIENCE OF NHL HOCKEY: Newton’s Three Laws of Motion (Grades 9-12)

##### Objective:

1. Students will design and carry out a demonstration of Newton’s first law of motion. 2. Students will design and carry out an investigation of Newton’s second law of motion. 3. Students will design and carry out a demonstration of the conservation of momentum and explain its relation to Newton’s third law of motion.

##### Introduction Notes:

**Science of NHL Hockey:** Newton’s Three Laws of Motion

Subject Area: Physics

Grade Level: High School Physics

Lesson Title: __Newton’s Three Laws of Motion__

## National Science Education Standards:

## Science as Inquiry: 9–12

Motions and Forces: 9–12

Suggested Prior Knowledge: concepts of mass, velocity, and acceleration; lab techniques of measuring mass, distance, and time. Note that students might more easily grasp the concepts in this video if they have already viewed the video *Kinematics*.

Purpose and Introduction: This video focuses on the actions involved in playing the game of hockey. Although all sports are subject to Newton’s three laws of motion in one way or another, hockey shows especially clear examples. The activity will help students to understand Newton’s three laws of motion and how they relate to the conservation of momentum.

## Key Vocabulary

* conservation of momentum*—constancy of the total moment of a closed system; derived from Newton’s third law.

* impulse*—force applied over a time interval; equal to the change in momentum, or the product of mass and change in velocity, of an object the force acts on.

* inertia*—resistance to a change in motion of a moving object or a stationary object.

* momentum*—the product of an object’s mass and its velocity.

* Newton’s first law of motion*—Objects remain at rest or in motion with a constant speed and direction unless acted upon by a force.

* Newton’s second law of motion*—The net force applied to an object is equal to the product of the object’s mass and its acceleration;

*F*=

*ma*(net force = mass × acceleration).

* Newton’s third law of motion*—Every action has an equal but opposite reaction. For instance, in a collision between two objects, the forces acting are equal in magnitude and opposite in directions:

*F*

_{1}= –

*F*

_{2}.

## Objectives:

- Students will design and carry out a demonstration of Newton’s first law of motion.
- Students will design and carry out an investigation of Newton’s second law of motion.
- Students will design and carry out a demonstration of the conservation of momentum and explain its relation to Newton’s third law of motion.

** **

**Materials:**

- Safety goggles

- Hockey puck or bean bag

- Chalk

- Skateboard

- Bricks

- Spring scale

- Stopwatches

- Meter stick

- Tape or markers

- Ring stands

- String

- Blocks

- Spring

- Thread

- Scissors

## Procedure:

1. After students view the video, discuss with them Newton’s three laws of motion. Have volunteers summarize the presentation of inertia and conservation of momentum in the video, and point out examples of the three laws as they view the video again—perhaps in slow motion or with the sound muted. Emphasize to students that a hockey puck obeys Newton’s laws, just as colliding hockey players do. (The same is true for a ball in other sports, such as basketball, soccer, golf, or jai alai.) Focus on exploring each of the laws:

*How might a struck hockey puck demonstrate Newton’s first law of motion?**How might two hockey players demonstrate Newton’s second law of motion?**According to Newton’s third law of motion, how are forces applied between two colliding hockey players?**What is momentum?**What does it mean that momentum is conserved?*

2. Lab protocols should be followed incorporating safety equipment. Goggles must be worn at all times.

3. Guide students to design investigations for Newton’s three laws. Allow students to examine the materials available. Alternately, you might be able to borrow field hockey or street hockey equipment from the physical education department for students to use in the gym, cafeteria, or parking lot. The following are some questions to help focus students’ plans:

*What is true of a moving object? How can this tendency be shown by dropping an object?**What law describes the behavior of an object acted on by a force?**How can this law be demonstrated with a constant force and variable mass?**What is true of two bodies forced apart by an expanding spring?*

4. The procedures suggested here are simple demonstrations of Newton’s three laws. However, students may prefer to construct other demonstrations or activities using these materials. For instance, the hockey puck can be placed on the skateboard for a demonstration of Newton’s first law. If the skateboard is rolled and brought to a stop, the puck will continue in motion and slide off the skateboard. Students should be encouraged to think of alternative ways the equipment they have can be used to demonstrate Newton’s laws.

5. The hockey puck (or beanbag) and chalk are useful for a simple demonstration of inertia. One student walks at a constant, moderate speed and tries to drop the puck onto a chalk mark. Dropping the puck when it is directly over the chalk mark will not work. The student must drop the puck slightly before reaching the mark. Students should be able to observe that the puck hits the mark at the same time the student passes the mark. Students record and analyze their results to explain how the law of inertia (Newton’s first law) is involved.

6. Students might demonstrate Newton’s second law using the skateboard and bricks to form a body with a fixed mass. Encourage students to use the spring scale to measure the variable accelerating force. They can use the meter stick, markers, and stop watches to measure the speed of the accelerated body and the time the force acts. Students might need to practice pulling the loaded skateboard with a constant force. They can measure the final speed of the skateboard or its average speed while it is accelerating. Either method will demonstrate Newton’s second law.

7. Like two colliding hockey players, unequal masses forced apart by an expanding spring provide a simple example of conservation of momentum. Suggest students suspend two blocks on strings of the same length from the ring stands, as pendulums. Then instruct students to compress the spring and tie it with thread to maintain the compressed state. Students should then firmly attach the spring to the side of one of the blocks between the two blocks, being sure to measure the mass of that block including the spring. Students should then cut the thread without disturbing the blocks, which may take practice. Students should recognize that the more massive block will have the lesser velocity. If the arcs the blocks swing are small, the distance each block recoils is proportional to its velocity. Students should be able to verify that momentum is conserved, and they should be able to give a clear explanation of how conservation of momentum is related to Newton’s third law.

8. As a follow-up activity, have students research deceleration in skating. How does a skater increase friction to come to a sudden stop? What is the maximum deceleration possible? Students can prepare posters or slide shows and share them with the class.

## Additional Resources:

• http://www.mdsci.org/science-encounters/Demo/CupandCoin.html

• http://www.teachersdomain.org/resource/lsps07.sci.phys.maf.airtrack/

• http://www.usahockeymagazine.com/article/2009-08/science-hockey

• http://www.dummies.com/how-to/content/physics-understanding-newtons-first-law-of-motion.html

• http://science.discovery.com/videos/100-greatest-discoveries-shorts-laws-of-motion.html

**Student Worksheet for Newton’s Three Laws of Motion**

** **

Experiment Title: ______________________Date: ________Name: ______________________

Student Hypothesis: _____________________________________________________________

Materials:

- Safety goggles

- Bean bag

- Chalk

- Skateboard

- Bricks

- Spring scale

- Stopwatches

- Meter stick

- Tape or markers

- Ring stands

- String

- Blocks

- Spring

- Thread

- Scissors

Procedure:

Wear safety goggles for all lab work.

** **

Data and Observations:

Analysis of Data:

Conclusions: