Download Gravity! What the deal?

Primary Type: Lesson Plan
Status: Published
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Resource ID#: 128867
Gravity! What the deal?
This lesson teaches the students how distance and mass affect gravity in a system using centripetal force. This is best done when correlating to
the formation of the solar system.
Subject(s): Science
Grade Level(s): 6, 8
Intended Audience: Educators
Suggested Technology: Internet Connection, Smart
Phone/Tablet
Instructional Time: 1 Hour(s) 30 Minute(s)
Keywords: gravity
Resource Collection: FCR-STEMLearn Physical Sciences
ATTACHMENTS
CentripetalForce.docx
Gravity.docx
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will understand that as the distance of objects increase the force of attraction is weaker.
Students will understand that as the mass of the object increase the force of attraction is greater.
Students will be able to explain that the force of gravity causes the planets to move in their elliptical orbits.
Prior Knowledge: What prior knowledge should students have for this lesson?
A. Force is a push or a pull.
B. Some forces act through physical contact, while others act at a distance.
C. The Solar System contents and the basic circular motion of the planets around the sun
Guiding Questions: What are the guiding questions for this lesson?
How does mass and distance affect the force of gravity and the motion of objects in the solar system?
Teaching Phase: How will the teacher present the concept or skill to students?
Students will define gravity, mass, and distance. With their partners they will check their understanding and make adjustments. Students will be randomly chosen to
share and then definitions are redirected if misconceptions found.
Students will review centripetal force and the formation of the solar system from a solar nebula. Students will observe the spin of a ball on a string that the ball is
moving in a circle and this is held by the string and if the string is released (demonstrate this) the ball moves away in a straight line away from the orbit.
page 1 of 4 Prior to beginning the activity students will predict the outcome and result of the tests. (See centripetal force attachment)
Guided Practice: What activities or exercises will the students complete with teacher guidance?
Teachers will pass out the lab reports and review the data table. Reminding the students to use the labels on the table to completely understand what they are going
to use in their experiment. Students will be guided to notice the masses added to the bags and the distances. Probing the students to understand how will the distance
be determined? How will the accuracy of the spin be determined? How many masses are equal to "moderate" and "heavy"?
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
Students will complete the bag swings with the no mass, moderate masses, and heavy masses. Measure the force of the masses with a spring scale. Students will
also compare these swings and masses with different distances.
As the students review their data table they must review what the data table expects and their groups.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
Students will collaborate to finalize their data with their group and write their conclusion. Students will then be given sticky notes and then leave their materials at
their desk. The groups will rotate and review the information from another group. On the sticky notes, the students will write a positive note and any questions they
have about that group's data. Students will repeat this until they return to their station and materials. Students will then review their sticky notes and make
adjustments before the data is compared to the class.
Students will nominate an individual to write the results of trial 1 on chart paper or on the board. Another student is chosen to complete the next trial, and this
continues until each group has added all the information to the collective information.
Students will then review the class data as a whole to notice the trends and similarity of the conclusions.
Summative Assessment
Students will document their attempts with the bag and different distances. Students will analyze their data and notice the as the mass changes the distance changes
the amount of force needed. Lastly, the students will compare the results of the activity to the movement of the planets.
Analysis Questions: answers provided in italics
1. Was there difficulty spinning the mass 1?
No, the low mass allows the spin to happen effortlessly.
2. Was there difficulty spinning the mass 5?
Yes, the heavy mass requires more force to spin.
3. How did the force measured on the spring scale change from mass 1 to mass 5?
There was an increase in the force (# will vary depending on the masses)
4. What is the difference in the spinning from mass 1 to mass 5?
As the mass increases the spinning becomes more difficult and the amount time needs to spin the object increases.
5. What does the rope represent in the demonstration?
The rope is providing centripetal force by a tension force, which represents the attractive force of gravity. The rope tension is a contact force, gravity is a noncontact force, but both can keep objects rotating in a circle and are affected by mass and distance.
6. Complete the following statements:
As mass is added...
the spin becomes more difficult.
As the distance increases...
the more unstable the spinning becomes and there is less control over the object.
7. Think! The planets are held by a force and move in an orbit around the sun. Using the ideas learned in this activity explain how gravity, mass, and distance effected
objects orbiting in the solar system.
The closer planets have a stronger gravitational attraction to the sun due to the distance. This was exhibited by the spinning of the bag at the close distance. The
larger objects in the outer solar system have a strong attraction due to the masses. However, the distance from the sun does cause some reduction in the
gravitational attraction. This was illustrated in the unstable and difficulty spinning of the heavy masses and longer distances. Gravity was represented by the rope
attached to the bag, which is the centripetal force.
Formative Assessment
Students will identify the definition of mass, distance, and gravity. Students will think it, pair it, and share it. The teacher circulates listening to responses. After the
students have shared they will randomly be asked to share aloud and misconceptions addressed.
Feedback to Students
Gravity is the attraction between objects.
Mass is the amount of matter in am object.
Distance is a measure of length from a single point to an end point.
As the teacher circulates, student understanding of mass vs. weight, matter, and gravity are probed. Sample questions:
How is mass different than weight?
What is the heavy feeling?
As you stand closer to someone, do you feel "attracted"?
page 2 of 4 ACCOMMODATIONS & RECOMMENDATIONS
Accommodations:
Learning disabled students: Shortened written response, scaffolding during the activity
Gifted: Research centripetal force and provide an explanation of how this activity is similar to this force. After viewing the YouTube video Centripetal Force Board - Sick
Science! #191, the students can provide a further explanation of this demonstration and design an experiment to demonstrate this centripetal force with as many cups
as possible.
Extensions:
Students with access to tablets could record the results and then build a presentation to compare the spins of the lower versus heavy masses and small versus large
distances.
In order to fully explain Newton's laws, the students can watch the YouTube video Centripetal Force by Planet NutShell, which explains the dynamics of a ball spinning
on a string.
Students learning more about the calculations involved in centripetal force can use the Phet Simulation Gravity and Orbits and/or watch the YouTube video Fc and Fg
with Planets by Steve Epperson.
Suggested Technology: Internet Connection, Smart Phone/Tablet
Special Materials Needed:
Rope divided into 6 meter sections - one per group
Metal hiking clips - one per group
Reusable grocery bag with 2 handles - one per group
Weights - 16.9 oz water bottles with between 1 and 12 per group (the weight can be different but consistent between groups)
lab reports and pencils - one per student
meter stick - one per group
masking tape
stop watches - one per group
Further Recommendations:
The bag should be attached to the hiking clip by the handles. If you're worried about the thinness of the handles, they could be tied together then the clip attached
through the holes and around the new knot. One student should spin while the others observe from a distance. The spinner will have difficulty determining the control
of the spin and steadiness of the bag during the spin.
The water bottles are an easy option that can be used for masses, however, if you have another set of masses that will be consistent and are readily available to use,
the activity page can be adjusted.
Spring scales could be used during the spins to measure the amount of force needed for each mass. This will require a spring scale with a large range, due to the
amount of mass used.
Adapting this lesson for higher grade levels, the students can review the centripetal force videos in the extension and go to the Phet simulation site. Also, have
students caluclate the forces in use during the spins.
Additional Information/Instructions
By Author/Submitter
Removing the whole group data share or group rotation can reduce the time to one hour.
SOURCE AND ACCESS INFORMATION
Contributed by: Rachel Keene
Name of Author/Source: Rachel Hill
District/Organization of Contributor(s): Marion
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
SC.6.P.13.2:
SC.8.E.5.4:
Description
Explore the Law of Gravity by recognizing that every object exerts gravitational force on every other object and that
the force depends on how much mass the objects have and how far apart they are.
Explore the Law of Universal Gravitation by explaining the role that gravity plays in the formation of planets, stars, and
solar systems and in determining their motions.
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