##
* *Reflection: Developing a Conceptual Understanding
Newton's 2nd Law: Balloon Racers - Newton's Law Expo (6 of 9) - Section 3: Student Activity

The best strategy for teaching Newton's 2nd Law that I have found, is to focus on the relationship between force (F), mass (M), and acceleration (a); which can be expressed as the formula F=ma or force (F) equals mass (m) times acceleration(a). In other words the force placed on an object is based on the object's mass and the rate of speed it is traveling.

In the prior lesson Newton's 2nd Law Demonstration, the students built a **variable strip.** This allows them to manipulate the three variables contained within Newton's 2nd Law.

To build, cut three holes (about the size of a quarter) at each end and in the middle of a sentence strip. Label each hole as mass, force, and acceleration (in that order). A student can then insert their finger into the hole representing the variable they wish to remain constant. By placing their finger in the other hole they can raise or lower that value and the third variable reacts accordingly (either high or lower). So if force remains constant, an increase in acceleration requires a decrease in mass. In Newton's 2nd Law Demonstration each student must present their variable strip to their elbow partner and explain how the three variables interact.

*How to teach Newton's 2nd Law*

*Developing a Conceptual Understanding: How to teach Newton's 2nd Law*

# Newton's 2nd Law: Balloon Racers - Newton's Law Expo (6 of 9)

Lesson 6 of 12

## Objective: Students will be able to test Newton's 2nd Law of Motion using a balloon race.

This lesson is based on California's Middle School Integrated Model of NGSS.

MS-PS2 Motion and Stability: Forces and Interactions

**PE**: MS-PS2-2 - Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object.

**DCI**: PS2.A - The motion of an object is determined by the sum of the forces acting on it; If the total force the object is not zero, its motion will change (Newton's 1st Law). The greater the mass of the object the greater the force needed to achieve that same change in motion. For any given object, a larger force causes a larger change in motion (Newton's 2nd Law).

**Science and Engineering Practices **(7) Engaging in Arguments from Evidence

**Crosscutting Concept** (2) Cause and Effect

This activity can be used as a stand alone lesson or can be placed with eight other lessons, designed as an exposition to be experienced over three days.

Newton's Laws Expo contains:

- Coin Activity (1st Law)
- Hammer/Nail Activity (1st Law)
- Greek Waiter Tray (1st Law)
- Penny on a Coat Hanger (1st Law)
- Ping Pong Ball Activity (2nd Law)
- Balloon Racer (2nd Law) (this lesson)
- Paper Clip Racer (2nd Law)
- Skateboard Activity (3rd Law)
- Newton's Cradle (3rd Law)

I have also developed three demonstrations of Newton's Laws

Demonstrations

With this lesson, students engage in a short (eight minute) activity designed to demonstrate one of Newton's Laws. Balloons race across suspended fishing line, showing that the balloon with the lower mass will travel faster then a weighted balloon (**MS-PS2-2**). When a constant force is applied (inflated balloon), the object with the least mass will have the greatest acceleration (**PS2.A)**. It will be the student's responsibility to use evidence recorded during the activity to determine that Newton's 2nd Law is being expressed, demonstrating the relationship between force (F), mass (m), and acceleration (a) (**SP7**). Each activity has been carefully chosen to replicate a specific effect (**CCC**).

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#### Set-up

*120 min*

There are a few more materials needed for this activity, but they are easy to obtain and relatively inexpensive.

- 100 lb tension fishing line
- Cheap metal coat hooks (2) or eyebolts(4)
- Rope clips(4)
- Small pulleys(2)
- Silicon grease
- Balloon rockets (similar to ballon animals, but wider)
- Balloon pump (optional)
- Binder clips (to hold an inflated balloon closed)
- Pennies (I've also used paper clips - any small weighted object will do)
- Clear tape

Each group receives four balloons, two for each race. Using a balloon pumps help the students inflate the balloons to the proper and consistent size. BEWARE popping balloons! Binder clips help the students keep the balloon inflated until ready to race.

.

Rig Set-Up

Run 2 lines of 100 lb tension fishing line across the classroom. Cut two straws in half (lengthwise) and thread both halves on each line (see photo).

Using a rope clip, attach one end of the line to the wall. At the opposite wall, attach a small pulley, run the fishing line through the pulley and attach a weight (sand filled water bottles - see photo).

I purchased some cheap metal coat hooks and bolted them to the walls of my classroom. I kept them high enough so students can walk underneath. Another option would be to run the fishing line across the classroom and attach them to the end of desks. The weight will keep the fishing line taunt as the kids work with the lines. Use a rag or paper towel to grease the lines with silicon grease (helps reduce friction). Mark a point on the fishing line approximately 3 meters from the start. I stick little flags in the ceiling to designate the three meters (serves as a starting line).

Print out a copy of the Station Markers. Tape 'Station 6' marker card down to the desk where you intend students will conduct this activity. Each station marker identifies where the activity will take place and provides directions for completing the activity.

Print out a copy of Newton's Laws Exposition packet for each student. The packet includes directions and questions to answer. If you are performing this lesson as a single activity you will only need to print out Activity 6.

This activity is designed to accompany other Newton's Laws Activities. I run this unit as a three day exposition. Day 1 is reserved for showing all the students the nine activities. Days 2 and 3 allow for an eight minute rotation. I typically have my students experience five activities (40 minutes) on Day 2 and four activities (32 minutes) on Day 3 followed by a recap of the events.

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#### Student Activity

*8 min*

Newton's Second Law will be in effect for this lesson. Newton's Second Law states that acceleration (a) is based upon force (F) applied to the object and the mass (m) of the object. A change in force or mass will change the object's acceleration. This law can be summed by the formula F=ma (Force = mass X acceleration).

Students will not know what specific law of motion they will be experimenting with. They will have to record what they see, gather evidence, and defend their thinking about what law is being manipulated.

Directions

- Inflate two balloons of unequal size (one small and one large).
- Tape each balloon to the straws.
- Release at the same time.
- Record your observations

- Inflate two balloons of equal size (same size).
- Tape 5 large paper clips to one balloon.
- Tape one small paper clip to the other balloon.
- Release at the same time.
- Record your observations

**Student Work Sample**

#### Resources

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#### Extensions

*45 min*

Newton's Law are expressed in a multitude of ways in the English language because Newton's original text ' Philosophiæ Naturalis Principia Mathematica', often referred to as the 'Principia', was written in Latin (as were all scientific articles in that time) and translated into English. As such, there are many different translations, causing confusion with students.

I teach Newton's Three Laws using this translation.

- An object in motion will reamin in motion and an object at rest will remain at rest - unless acted upon by another force.
- Acceleration is based on force and mass (F=ma).
- For every action there is an equal and opposite reaction.

To assit in teaching Newton's Law before this lesson is taught, I have included three Powerpoint lessons:

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- UNIT 1: First Week of School
- UNIT 2: States of Matter
- UNIT 3: Periodic Table
- UNIT 4: Atomic Structure
- UNIT 5: Chemical Reactions
- UNIT 6: Forces
- UNIT 7: Density and Buoyancy
- UNIT 8: Motion
- UNIT 9: Solutions
- UNIT 10: Earth, Moon, and Sun
- UNIT 11: Solar System
- UNIT 12: Engineering and Design

- LESSON 1: Newton's 1st Law: Coin Activity (Inertia) - Newton's Law Expo (1 of 9)
- LESSON 2: Newton's 1st Law: Hammer, Nails & Inertia - Newton's Law Expo (2 of 9)
- LESSON 3: Newton's 1st Law: Greek Waiter Tray - Newton's Law Expo (3 of 9)
- LESSON 4: Newton's 1st Law: Penny on a Coat Hanger - Newton's Law Expo (4 of 9)
- LESSON 5: Newton's 2nd Law: Ping Pong Ball Activity - Newton's Laws Expo (5 of 9)
- LESSON 6: Newton's 2nd Law: Balloon Racers - Newton's Law Expo (6 of 9)
- LESSON 7: Newton's 2nd Law: Paper Clip Racers - Newton's Law Expo (7 of 9)
- LESSON 8: Newton's 3rd Law: Skateboard Activity - Newton's Laws Expo (8 of 9)
- LESSON 9: Newton's 3rd Law: Newton's Cradle & Expo (9 of 9)
- LESSON 10: Newton's 1st Law Demonstration
- LESSON 11: Newton's 2nd Law Demonstration
- LESSON 12: Newton's 3rd Law Demonstration