Newton's 1st Law: Greek Waiter Tray - Newton's Law Expo (3 of 9)
Lesson 3 of 12
Objective: Students will be able to experiment with centripetal force (explained by Newton's 1st Law) while using a Greek Waiter's Tray.
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) (today's lesson)
- Penny on a Coat Hanger (1st Law)
- Ping Pong Ball Activity (2nd Law)
- Balloon Racer (2nd Law)
- Paper Clip Racer (2nd Law)
- Skateboard Activity (3rd Law)
- Newton's Cradle (3rd Law)
I have also developed three demonstrations of Newton's Laws
With this lesson students will engage in a short (eight minute) activity designed to demonstrate one of Newton's Laws. A tray holding a glass of water will be spun around without spilling any water. When a force is applied at a right angle to an object a centripetal force is produced (MS-PS2-2). The students will learn that if the applied centripetal force is not great enough the cup of water will not be pinned down to the tray (PS2.A). It will be the student's responsibility to use evidence recorded during the activity to determine that Newton's 1st Law is being expressed (SP7). Each activity has been carefully chosen to replicate a specific effect, specifically applied to centripetal forces (CCC).
- Greek Waiter's tray (see how to build it below)
- Small paper cups
Directions for building a Greek Waiter Tray
- Select a piece of plywood at least 24 inches square.
- Drill a small hole in the approximate center.
- Measure 11 inches from the center and place a mark.
- Continue repeating step 3 until enough marks form a rough circle.
- Use a saw to cut the plywood circle.
- Insert a long metal threaded dowel in the center circle and secure with locking washers and bolts/
- Bend the opposite end of the metal dowel into a handle and cover with tape.
If building a Greek Waiter's tray is too much, Steve Spangler demonstrates a version that will work for this lesson.
Print out a copy of Station Markers and set up your work stations around the room (tape Station 3 marker card down to where students will conduct this activity). Each station marker identifies where the activity will take place and provides directions for completing the activity. I send this activity outside due to flying water cups.
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 3.
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.
Newton's First Law of Motion will be in effect for this lesson. Newton's First Law states that an object in motion will remain in motion and an object at rest will remain at rest, unless acted upon by another force. If that force acts at a right angle then the motion observed will be in a circle, this force is known as a centripetal force.
Students will not know what specific law of motion they will be experimenting with. They have to record what they see, gather evidence, draw a conclusion based upon that evidence and argue about what law is being manipulated.
- Place a cup of water (half full) onto the platform.
- Gently swing the platform back and forth, gradually increasing speed.
- Continue to swing the platform until you have achieved a complete loop without spilling the water.
Student Work Sample
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. All of these years later, we still have differing definitions.
I teach Newton's Three Laws with this translations.
- 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 assist in teaching Newton's Law before this lesson is taught, I have included three Powerpoint lessons: