## Description

“

Having students plan and carry out an investigation they created is powerful! The first thing you need to have going into this activity is patience and knowing that the data collected won’t be the prettiest. Allowing students to design an experiment also takes time, that’s why this resource is 3-5 days long. However, the depth of learning that occurs is amazing!!! The benefits are real, worth it, students are engaged and have much more buy-in. Students discover that all objects fall towards earth at 9.8m/s/s regardless of mass, if air resistance isn’t a factor. They start by thinking about the question, ** “Can objects with different masses fall towards Earth at the rate of surface gravity (9.8m/s/s) in an open system?”** Much like Galileo did! Students also learn that mass dictates how much gravity there is on other planets.

**Day 1: **

**1hour 50-minute Block**

**Engage:** **20 minutes**

**Explain:** **20 minutes**

**Explore:** **20 minutes**

**Planning Investigation:** **30-40 minutes**

**Day 2: **

**1hour 50-minute Block **

**Carrying Out Investigation:** **45 minutes**

**Extend 1:** **20 minutes**

**Extend 2:** **20 minutes**

**Evaluate:** **30 minutes**

Day 3:

Tie up loose ends and debrief

**This resource includes the following:**

-PDF Student Copy of Lab

-Editable Microsoft Publisher Version

-Google Doc Copy of the resource

-PowerPoint with the key, rules and student tips for classroom management

-14 pages of very detailed teacher notes

**There are two options for data collection with this investigation:**

**Option 1-**Use the equation ** acceleration = 2(distance) ÷ time squared or a=2d/t²**, where students collect the time it takes for the objects to fall two meters. The goal is for students to discover that the heavier objects will fall close to the rate of surface gravity 9.8m/s/s and lighter objects will fall much slower due to air resistance having a greater affect. Like Galileo discovered, despite large differences in mass, objects will fall very close to surface gravity unless they are extremely light like the Styrofoam bowl I use. This is the question for the investigation,

*“Can objects with different masses fall towards Earth at the rate of surface gravity (9.8m/s/s) in an open system?”***Option 2-** Students observe which objects hit the ground first, with no math involved, similar to what Galileo did on the Leaning Tower of Pisa. This is the question for the investigation, *“Is mass a factor when objects fall towards earth in an open system?”*

My coleague chose option 2 and it was very successful. I chose option 1 with success as well.

**NGSS Performance Expectations:**

-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. MS-PS2-2

-Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects. MS-PS2-4

**NGSS Disciplinary Core Ideas: **

-Gravitational forces are always attractive. There is a gravitational force between any two masses, but it is very small except when one or both of the objects have large mass—e.g., Earth and the sun. (MS-PS2-4)

-The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion. (MS-PS2-2)

-All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared. (MS-PS2-2)

**NGSS Science and Engineering Practices: **

-Modeling -Planning and carrying out an investigation -Analyzing and interpreting data -Using Mathematics and Computational Thinking -Obtaining, evaluating and communicating information -Claim Evidence Reasoning

**NGSS Cross Cutting Practices: **

-Patterns

-Cause and Effect

-Systems and System Models

**Engage (Day 1):** First show the YouTube video “Brian Cox visits the world’s biggest vacuum chamber – Human Universe: Episode 4 Preview – BBC Two” starting at 2:48, till about 3:45, ** don’t show the whole clip!** This ensures the phenomena is a discrepant event. I want the students to wonder why it happened and then search for the answer on their own in the “Explore” segment. Students observing feathers and a bowling ball fall at the same rate is an attention grabber!

Students then fill in the chart of what they observed and what they wonder. Based on what they observed they draw a model (SEP #2) of what they think happened. In NGSS, a model is a simplified representation of a system that can explain and help make predictions regarding phenomena. I encourage the students to make models that are mental representations of what can’t be seen by just observations. Most of them say air resistance was a factor and that’s ok! The only force acting on the feathers and bowling ball is gravity because it’s within a closed system.

**Explain:** Students then do research on why they both fell at the same rate and they look up what surface gravity is on earth (9.8m/s/s). They will find that all objects fall at the rate of 9.8 m/s/s on earth if air resistance isn’t a factor

**Explore:** At this point I introduce the 5 different objects the students will be using in the investigation. I use a **steel marble, whiffle ball, bean bag, piece of wood and a Styrofoam bowl.** I tell the students they will plan and carry out an investigation (SEP #3) that answers the question, ** “Can objects with different masses fall towards Earth at the rate of surface gravity (9.8m/s/s) in an open system?”** (MS-PS2-4).

**Planning Investigation:** Students design their procedure and data table based the equation ** a=2d/t²**.

**Explore (Day 2):** After tips and examples I give the students, they redesign their data tables and procedures.

**Carrying Out Investigation:** Once I approve each group’s data table and procedure, I allow them to gather their materials and begin.

**Extend 1:** Hopefully at this point, students understand that all objects fall towards earth at the rate of 9.8m/s/s unless air resistance is a factor. We then look at surface gravity on different planets in the “Extend” portion. I Segway from the “Explore” to the “Extend” by looking at good examples of group’s data. In every class, at least 1-2 groups will calculate some objects close to 9.8m/s/s! Anything calculation from 7m/s/s to 12m/s/s is accurate data. I also show examples of data that is way off, and you will see a lot of that. Like I said, the data won’t be the prettiest. However, this creates discussion about experimental design, which is very meaningful and powerful.

For the “Extend”, students graph Surface Gravity in m/s/s on the Y-axis and the planets on the X-axis. This is where we address how larger planets with more mass have greater gravity.

**Extend 2: **Students then take learning about gravity on different planets a step further by looking at how gravity and mass affect the Earth’s orbit around the sun. The PhET simulations show how the movement of the Earth and moon relates to gravity. Students manipulate the mass of the Earth, Moon and Sun to see how gravity and orbit are affected.

**Evaluate:** In the evaluate section, we revisit the question,

These forces lessons from my store are a great scaffold for this resource:

**MS-PS2-1 & MS-PS2-2: STEM 5E NGSS Balloon Cars Lab Engineering**

**NGSS MS-PS2-2: STEM 5E Paper Airplane Competition Forces Interactions**

**MS-PS2-2: 5E NGSS Collision Lab Motion Forces Close Reading & Notes CER Article**

**MS-PS2-2: STEM Roller Coaster Lab & Card Sort Engineering Design Process**

**MS-PS2-1: STEM Bottle Rockets PowerPoint Graphic Organizer Close Reading & Notes**

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