Lesson 2 - Gravity, you will fall for it

Lesson overview

In this lesson you will:

use your investigative and communication skills to create a scatter plot that explores the relationship between variables in the Law of Universal Gravitation.

Overview

Duration: 2:03

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Intentions and criteria

Learning Intentions:

To know that all objects have a mass and therefore have gravity.
To understand the relationship between variables in a fair test.
To be able to communicate data as a graph and to identify any trends on this graph.

Success Criteria:

I have used my research and investigative skills to learn how to construct a scatter plot.
I can analyse graphs and equations and communicate any relationships.

Challenges

Description of must do, should do and could do activities

Challenges

Some of the activities in this lesson are must do activities. These are also called a mini challenge. Please have a go at the should do activities and reach out to your teacher if you need assistance. You could also spend some extra time problem solving a solution to these challenges. Finally, there are super challenge activities, the could do activities. We strongly encourage you to try these.

Activity 1: Graphing your data

Last lesson you explored the "Law of Universal Gravitation" and constructed a table of the data you got when you changed one variable.

Now we are going to graph your data in a line graph (x-y scatter).

You have TWO choices for how you complete this activity. Only complete the activity ONE of these ways.
1. Complete this task online using Excel or Google Sheets.
2. Complete this task in your exercise book or folder by hand.

Help, I lost my work or I didn't do Lesson 1!

If you don’t have access to data from the previous lesson you can use this example one.

Example data table document

Choice 1: Graphing online using Excel or Google sheets

The first step is to create a third column in your table and convert the Force (N) value into a version of scientific notation that works in Excel and Google.
- This is because the spreadsheet software doesn't understand this number 7.42 x 10^-6 as a number, it thinks it is text.
- Convert each number using the formula below so that it looks like this example:
  1. 1. - 7.42 x 10^-6 turns into 7.42E-06.
      - Number before the X, followed by capital E, followed by whatever the power of 10 is, but add a zero.
- So, using this method, 1.76 x 10^-5 will turn into 1.76E-05 for example.
Next, create a new Excel or Google Sheets file. Don't forget to label the file something useful so you can find it again. You could use Gravity Lesson 2 Scatter graph as the name for example.
Copy the information you need from your data table into the spreadsheet.
Create a scatter graph using the data.
- Need help? Watch Creating a Scatter Plot in Excel on YouTube to get a brief introduction to how to create a graph in Excel or read and watch how to create your graph in Google Sheets on the Google website.
Save your document so that it is ready to submit to your teacher.

Choice 2: Graphing by hand

The first step is draw out your blank graph on some grid paper.
- Hint: The independent Variable goes on the x-axis (this is the variable that you changed).
- Look at your values for the y-axis and work out what scale you will use. Remember that the distance between each mark has to be the same.
Plot each of your data pairs as a point on your scatter graph.
Hand draw a line of best fit.
If your work is not in your exercise book or folder for your teacher to see later, take a photo of your work ready to submit to your teacher.

Help, this activity is talking about scientific notation and I don't remember what that is or I forgot how to use it.

Revise scientific notation by going to the Maths is fun website. Read the information and then try the quiz at the end.

Activity 2: Analysing your data

Use your graph to answer the following questions in your exercise book or folder:

Looking at the 2 graphs, which trend best matches your data? 1 or 2?

Graph 1: Directly proportional

Graph shows straight line running through points, (0,0), (1,1), (2,2), (3,3), (4,4)

Graph 2: Inverse square

What does this say about the relationship between the variables? (How does changing one impact the force?)

What relationship can be seen between your chosen variables? How have you come to this conclusion?

Activity 3: Formulas are a mathematical model

Like we saw in Lesson 1, Newtons Law of Gravitation can be represented mathematically as shown below:

Not to worry, you don't need to remember the formula!

NewtonsLawGravitation.png (CC BY-SA)

This equation represents a mathematical model.

Answer the following questions in your exercise book or folder.

What relationship/s does this equation ‘say’ about the variables which impact the force?

Hint

Write statements similar to the following.

If you increase r then ...
If m1 or m2 decrease then ...

Do the results of your data/experiment support this model? Would you need more information to be more certain? Why or why not?

Does the data you gathered fit ‘Newtons Law of Gravitation? What evidence can you provide to support your answer.

Using the simulation what further investigation would you need to do to be more confident is your assessment of the model?

Extension

You can try to answer these question in your exercise book or folder. You will need to use the Gravity Force Lab simulation again to help you with the first question.

The letter G is used to represent ‘Universal Gravitational Constant’ with a value of 6.67 × 10-11 Nm2kg-2. Using the simulation can you verify this value? Support your answer using data and calculations.

By using Newtons 2nd Law (F=ma) and his equation for universal gravitation (see above) you can create an expression to calculate gravity.

Derive an expression for the acceleration due to gravity using both these equations (show all your working).

Handing in your work

Don't forget to hand in the work you completed today!

Your teacher will have told you to do one of the following:
- Upload any digital documents you created and any photos you took of your written work to your Learning Management system (MS Teams, Google Classroom for example).
- Email any digital documents you created and any photos you took of your written work to your teacher.

Make sure you keep any hand written work you did in your exercise book or folder as your teacher may need to see these when you are back in class.

Student reflection

Show how you feel about today's learning.

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