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Gravitational Field

7.1.6 Gravitational Field LO (a)

Think about it: How can two objects exert attractive forces on each other when they are not in contact with each other?

Every object sets up a gravitational field around itself due to its mass. When two objects enter each other’s gravitational fields, they will be attracted towards each other.
Hence, a gravitational field is a region of space in which any object that lies in it experiences a gravitational force towards the object that creates the field, due to its mass.

(For your information, magnetic fields and electric fields are also examples of force fields.)

7.1.6.1 Inquiry:

A gravitational field is invisible and thus is represented by imaginary field lines on paper. How would the Earth’s gravitational field (over both near and large distances from Earth) look like?

1) Using the simulation later, drag the red test mass to the outer most series of blue dots and play and simulation. Every time the field lines are drawn and contact Earth's surface, the simulation will pause. When that happens, drag the red mass to a new position to draw the field line and click play to continue to run the simulation. repeat these steps until all outer most series of blue dots have been drawn with the field lines. The green vectors represent the field vectors while the red lines represent the field lines near the Earth’s surface. Compare with the picture below;

•    The gravitational field near Earth’s surface is uniform
•    The field lines should be drawn parallel to each other and of equal spacing.

2)     Select from the drop down menu the option for Near_Earth_Surface. Using the same steps earlier, try to draw the RED field lines for this case. Compare with the picture below.
near earth surface

•    The gravitational field around Earth is non-uniform.
•    The field lines should be drawn radially pointing towards the centre of Earth.

3)     Select from the drop down menu the option for Outer_Space. Using the same steps earlier, try to draw the RED field lines for this case. Compare with the picture below.

outer space

•    The gravitational field around Earth is non-uniform.
•    The field lines should be drawn radially pointing towards the centre of Earth.

4)     Finally, select from the drop down menu the option for very_outer_Space. Using the same steps earlier, try to draw the RED field lines for this case. Compare with the picture below.

very outer space

• The gravitational field around Earth is non-uniform.
• The field lines (use the red test mass to draw field lines) should be drawn radially pointing towards the centre of Earth.

What can you infer from the representations of these gravitational field lines? LO (e)

The closer the field lines, the stronger the gravitational field.
Near Earth’s surface, the field strength is approximately constant (around 9.81 m s^-2) and hence the gravitational field lines are almost equidistant from each other.
Over large distances from Earth, the gravitational field strength decreases as it gets further from Earth and hence the gravitational field lines space out further from each other.

7.1.6.2 Model:

Translations

Code	Language		Translator	Run

Credits

andrew duffy; lookang

http://iwant2study.org/lookangejss/02_newtonianmechanics_7gravity/ejss_model_gravity03_1/gravity03_1_Simulation.xhtml

Briefing Document: 🌎Earth's Gravitational Field Simulation Model

1. Overview

This document analyzes an online educational resource focused on visualizing and understanding Earth's gravitational field using a 2D JavaScript HTML5 applet simulation. The resource, hosted by Open Educational Resources / Open Source Physics @ Singapore, aims to help learners grasp the concept of gravitational fields through interactive exploration and visualization.

2. Main Themes and Concepts

Gravitational Fields: The resource introduces the concept of a gravitational field as a region of space where an object with mass experiences a gravitational force. It emphasizes that objects don't need to be in contact to exert these forces.
Quote: "Every object sets up a gravitational field around itself due to its mass. When two objects enter each other’s gravitational fields, they will be attracted towards each other."
Field Lines: The simulation uses field lines to represent the invisible gravitational field. The briefing highlights the visual characteristics of these lines and their relationship to field strength.
Quote: "A gravitational field is invisible and thus is represented by imaginary field lines on paper."
Field Vectors: The resource also mentions green vectors, which represent the field vectors.
Non-Uniformity: A key focus is on the non-uniform nature of the Earth's gravitational field, particularly over large distances. The simulation allows for exploration of this changing field.
Quote: "The gravitational field around Earth is non-uniform."
Uniformity Near Earth's Surface: Conversely, the simulation demonstrates that the field is nearly uniform near the Earth's surface.
Quote: "The gravitational field near Earth’s surface is uniform"
Relationship between Field Line Density and Field Strength: The resource explains that the closer the field lines are, the stronger the gravitational field.
Quote: "The closer the field lines, the stronger the gravitational field."
Radially Inward Field Lines: It is emphasized that the gravitational field lines around Earth should be radially pointing towards the center of the Earth
Quote: "The field lines should be drawn radially pointing towards the centre of Earth."
Simulation as an Inquiry Tool: The resource uses the interactive simulation as the basis of inquiry, encouraging users to drag a test mass and observe the resulting field lines.
Quote: "Using the simulation later, drag the red test mass to the outer most series of blue dots and play and simulation."
Constant Field Strength Near Surface: Near the Earth's surface, the field strength is approximately 9.81 m/s², and hence, the field lines are almost equidistant.
Quote: "Near Earth’s surface, the field strength is approximately constant (around 9.81 m s-2) and hence the gravitational field lines are almost equidistant from each other."
Decreasing Field Strength with Distance: Over large distances, the field strength decreases, reflected in the spacing out of field lines.
Quote: "Over large distances from Earth, the gravitational field strength decreases as it gets further from Earth and hence the gravitational field lines space out further from each other."

3. Simulation Functionality and Exploration

The simulation model has different options to select through a drop-down menu:

Near_Earth_Surface: The applet helps users visualize the uniform gravitational field with equally spaced field lines.
Outer_Space: This option shows the non-uniform, radially pointing field lines further from Earth.
very_outer_Space: This explores the gravitational field very far from the Earth, emphasizing the weaker force and more spread-out field lines.

The simulation prompts the user to drag a red test mass to specific locations (blue dots) to trace field lines, enhancing the learning experience by requiring active participation.

4. Key Facts and Observations

Field Strength and Line Spacing: The closer the lines, the stronger the field.
Near-Surface Field: The field is nearly uniform near the Earth's surface, with constant strength.
Large Distance Field: The field is non-uniform at large distances, and the field strength decreases.
Field Lines Direction: Field lines always point towards the center of Earth.
Simulation-Based Inquiry: The applet allows for an inquiry-based learning experience.

5. Supporting Resources

The resource also provides:

Embed Code: HTML embed code for integrating the simulation into websites.
Links to the simulation: Link to run the simulation.
Video Tutorial: A YouTube video link ("Field lines and field vectors video tutorial") for further explanation.
Pictures: Links to pictures showcasing various gravitational field representations.
Apps Link: Link to android version of the app.

6. Target Audience

The resource appears to be designed for Junior College level students, though the interactive nature and visual explanations may be valuable to a broader audience interested in introductory physics.

7. Technical Details

The resource is based on EasyJavaScriptSimulation.
It has various different names: Earth Field 2D JavaScript HTML5 Applet Simulation Model; ejss_model_gravity03_1.
It was created by Andrew Duffy and Lookang.

8. Conclusion

The provided resource offers an effective and interactive way to learn about Earth's gravitational field. The use of field lines, vectors, and an interactive simulation allows users to visualize and understand the concepts of uniform and non-uniform fields and how their strength varies with distance from Earth. The inclusion of supporting materials such as embed codes, video tutorials, and links to pictures further enhances the educational value of the resource. The resource seems effective at supporting inquiry-based learning.

Gravitational Fields Study Guide

Quiz

Instructions: Answer the following questions in 2-3 sentences each.

What is a gravitational field, and how is it created?
Why do objects with mass exert gravitational forces on each other, even when they are not in contact?
What is the relationship between the strength of a gravitational field and the distance from the object creating the field?
How are gravitational field lines used to represent the strength and direction of a gravitational field?
Describe how gravitational field lines are arranged near the Earth's surface.
How does the arrangement of gravitational field lines change as you move farther away from Earth?
What does it mean when field lines are close together?
What is the approximate value of the gravitational field strength near Earth's surface?
Explain why the Earth's gravitational field is considered non-uniform over large distances.
Briefly explain how the provided simulation can be used to visualize gravitational fields.

Quiz Answer Key

A gravitational field is a region of space where an object with mass will experience a gravitational force. It is created by every object with mass and extends outward from the object in all directions.
Objects with mass exert gravitational forces on each other because each mass creates a gravitational field around itself, and when these fields overlap, they exert forces on the objects within the overlapping region. The objects do not need to be in physical contact to experience this force.
The strength of a gravitational field decreases as the distance from the object creating the field increases. This means that objects experience a weaker gravitational force the further they are from the source of the field.
Gravitational field lines are imaginary lines that illustrate the direction and strength of the gravitational force. The direction of the line indicates the direction of the force, and the density of the lines indicates the strength of the field.
Near the Earth's surface, gravitational field lines are approximately parallel to each other and evenly spaced. This represents a nearly uniform field strength in that region.
As you move farther from the Earth, the gravitational field lines become radial, pointing towards the Earth's center. The spacing between the lines increases, indicating a weaker field strength.
When field lines are closer together, it indicates a stronger gravitational field, where objects will experience a greater force of attraction. The density of the lines directly corresponds to the field strength.
The gravitational field strength near Earth's surface is approximately 9.81 m/s², which is the acceleration due to gravity at that location. This value is also referred to as the gravitational acceleration.
The Earth's gravitational field is non-uniform over large distances because the field strength decreases as the distance increases. This causes the field lines to be more spread out, representing a weaker gravitational pull.
The simulation allows users to drag a test mass and trace the gravitational field lines by visualizing the path the mass takes under the influence of gravity. By repeating this process, a complete image of the field can be generated.

Essay Questions

Instructions: Answer the following essay questions thoroughly. Provide detailed explanations and examples to support your points.

Discuss the concept of a gravitational field as a force field. Compare and contrast it with other types of force fields (such as magnetic or electric fields) you might be familiar with, focusing on the similarities and differences in their properties and behaviors.
Explain how the provided simulation can be used to illustrate the concept of uniform and non-uniform gravitational fields. Describe the methodology a student might use when running the simulation and what key observations they should make to understand these concepts.
Describe the implications of non-uniform gravitational fields for objects at various distances from a massive body such as the Earth. How does this affect the forces experienced by satellites in orbit, for instance?
How does the visual representation of field lines assist in understanding the concept of a gravitational field? Discuss the use of field lines as a model and how they relate to the actual force experienced by objects within the field.
Explore the limitations of the 2D simulation provided, how it simplifies the real-world complexities of gravitational fields, and offer recommendations for how the simulation could be enhanced to provide a more detailed and accurate understanding of the concept.

Glossary of Key Terms

Gravitational Field: A region of space surrounding an object with mass in which any other object with mass will experience a gravitational force.

Field Lines: Imaginary lines used to visualize the direction and strength of a force field. The density of the lines represents the strength of the field, and the direction of the lines represents the direction of the force.

Uniform Gravitational Field: A gravitational field where the field strength is constant across the region, as approximated near the Earth's surface. Field lines are parallel and equally spaced.

Non-uniform Gravitational Field: A gravitational field where the field strength varies from place to place, common around a massive body over a large distance. Field lines are radial and space out as distance increases.

Test Mass: A small mass used in a simulation or experiment to probe the properties of a gravitational field without significantly altering the field itself.

Field Strength: A measure of the magnitude of the gravitational force experienced by an object within the field, often expressed as acceleration (m/s²).

Force Field: A region of space where a force is exerted on any object with the appropriate property (mass, charge, magnetic moment). Gravitational, electric, and magnetic fields are examples.

Apps

Cover art https://play.google.com/store/apps/details?id=com.ionicframework.gravity031app588830&hl=en

Picrtures

https://sg.iwant2study.org/ospsg/index.php/55
The closer the field lines, the stronger the gravitational field.

https://sg.iwant2study.org/ospsg/index.php/55
Near Earth’s surface, the field strength is approximately constant (around 9.81 m s-2) and hence the gravitational field lines are almost equidistant from each other.

https://sg.iwant2study.org/ospsg/index.php/55
The gravitational field around Earth is non-uniform.
• The field lines should be drawn radially pointing towards the centre of Earth.

Video

Field lines and field vectors video tutorial

https://youtu.be/MTY1Kje0yLg Gravity Visualized by apbiolghs

https://notebooklm.google.com/notebook/0ddd34ab-0877-4ae0-8812-9139c8735211/audio

imeline of Main Events (Based on the Source)

This source doesn't describe a chronological sequence of events in the traditional sense, but rather steps in an interactive simulation and the conceptual development it helps to facilitate. Therefore, I will structure it around the logical steps in the simulation rather than a strict linear timeline:

Conceptual Introduction: The resource begins by posing the question of how objects exert attractive forces without contact, introducing the concept of a gravitational field.
Gravitational Field Definition: The resource defines a gravitational field as a region of space where objects with mass experience gravitational force. It also provides context by mentioning magnetic and electric fields.
Inquiry-Based Learning: The resource structures learning around a series of inquiries.
Inquiry 1: Earth's Gravitational Field (General): Users are asked to use the simulation to draw field lines representing Earth's gravitational field at large distances. The simulation is designed to pause at each field line intersection with the Earth's surface. The expectation is that users discover that field lines point towards the center of Earth and are spaced out further the further they are from the Earth.
Inquiry 2: Near-Earth's Surface: Users use the simulation to draw gravitational field lines near the Earth's surface and notice that the gravitational field is uniform here. The user draws field lines that are parallel to each other and of equal spacing.
Inquiry 3: Outer Space: Users use the simulation to draw gravitational field lines in outer space, and are supposed to discover that that the gravitational field is non-uniform, with lines pointing radially towards the center of the Earth.
Inquiry 4: Very Outer Space: Users use the simulation to draw gravitational field lines very far away from the Earth, and are supposed to discover that that the gravitational field is non-uniform, with lines pointing radially towards the center of the Earth.
Inferences about Gravitational Fields: The resource guides users to make key inferences about gravitational field lines:
Field lines are closer together where the gravitational field is stronger.
Near Earth's surface, the field strength is constant, hence the equidistant field lines.
Over large distances from Earth, field strength decreases, hence the field lines are spaced out more.
Model & App: The resource references the simulation model and provides links to its web-based and app-based versions.
Supplementary Resources: It points to additional resources, such as a video tutorial about field lines and field vectors, and related simulations using EJS (Easy JavaScript Simulation).
Educational Context: The resource is embedded within a larger collection of open educational resources, indicated by the extensive list of other simulations and workshops available.

Cast of Characters

This source is primarily about the development and use of an interactive educational resource. Therefore, the "characters" are the individuals involved in its creation and promotion.

Andrew Duffy: Credited as one of the developers of the simulation (along with lookang). No specific biographical details are given, but they likely contributed to the conceptualization or coding of the simulation.
lookang: Listed alongside Andrew Duffy as a creator, suggesting they were instrumental in developing the simulation. The username also appears within the website indicating their role as a key contributor to the OER platform.
Francisco Esquembre and Félix J. García Clemente: Listed as part of the team running a Web EJS beta workshop on the webpage, indicating their association with the development of the EJS toolset that the resource uses.

Frequently Asked Questions about Gravitational Fields

What is a gravitational field, and how does it explain attraction between objects?
A gravitational field is a region of space around an object with mass where another object would experience a gravitational force. It's an invisible field created by every object with mass. When two objects are in each other's gravitational fields, they are drawn toward one another as they experience gravitational forces toward the center of mass of the source object creating the field. This explains how objects attract each other without physical contact.
How are gravitational fields represented visually?
Gravitational fields are often represented by field lines. These lines are imaginary and show the direction of the force a small test mass would experience if placed at that location in the field. The closer the field lines are to each other, the stronger the gravitational field strength is in that area. Field lines point toward the source object, as the force always attracts toward the center of the object.
What does a gravitational field look like near the Earth's surface?
Near the Earth's surface, the gravitational field is considered uniform. This means the gravitational force is approximately the same strength and direction at different locations in that region, and the field lines are shown as parallel and equally spaced. The field is approximately 9.81 m/s².
How does the Earth's gravitational field change as you move further away from the surface?
As you move further from Earth, the gravitational field becomes non-uniform. The field lines start to spread out, indicating that the gravitational force is decreasing in strength. The field lines are still radial, pointing towards the center of the Earth, but the spacing between them increases with distance.
What do field vectors and field lines represent in the simulation?
In the provided simulation, the green vectors represent the field vectors, showing the direction and relative strength of the gravitational field at each point. The red lines represent the field lines, which follow the path a small test mass would take under the influence of the gravitational force. The density of the field lines visually shows the gravitational field strength.
What does the simulation allow users to explore and learn about gravitational fields?
The simulation allows users to explore and understand how gravitational fields vary both near and far from Earth, drawing field lines and visualizing the field strength. Users can observe that near Earth's surface, the gravitational field is uniform, while at greater distances, it's non-uniform, showing the radial nature of the field. The simulation supports an inquiry-based learning process where students can draw and observe the field lines by moving the red test mass to see the changing field.
Besides gravity, what are some other examples of force fields?
While the document specifically discusses gravitational fields, it mentions that magnetic fields and electric fields are also examples of force fields. These fields also exert forces on objects, like charged particles in the case of electric and magnetic fields, without physical contact.
What are some of the other interactive simulations and educational resources offered by the same organization?
The organization provides numerous interactive simulations covering various topics, including moon phases, energy pendulums, collisions, friction, projectile motion, vector addition, and much more. They also feature resources for chemistry, math, and other fields, with simulations and activities for a range of educational levels and topics. They also provide information and workshops for educators using tools such as WebEJS to build their own simulations.