The Arizona STEM Acceleration Project

Earth’s Gravity and How it Affects Objects of Different Masses

Earth’s Gravity and How it Affects Objects of Different Masses

​

A 7th grade STEM lesson

Author: Georgina Matzkin

Date: 10-14-23

Notes for teachers

• This lesson takes place in a classroom for two hours.
• Students may work in groups of 3-4.
• Calculate your largest class and then see how many nuts, bolts, stopwatches, meter sticks, and mats you will need. You can reuse the materials each period.
• The mat is to protect the floor from dents.
• Note: I used 1.75 m for the distance (since that is what my table tops and meter stick measured together). However, you can use a different measurement and go as high as you can. If you go too low it might be difficult to see a difference.

List of Materials

​

Each group will need the following:

• 6 Nuts (¼-20) and 1 bolt (¼-20 x 2”)
• Stopwatch
• Mat for floor
• 1 meter stick

​

Standards

Science Standard:

​

​

Physical Science Standards:

7.P3U1.3 Plan and carry out an investigation that can support an evidence-based explanation of how objects on Earth are affected by gravitational force.

​

Science and Engineering Practices

●ask questions and define problems

●develop and use models

●plan and carry out investigations

●analyze and interpret data

●use mathematical and computational thinking

●construct explanations and design solutions

●engage in argument from evidence

●obtain, evaluate and communicate information

​

Cross Cutting Concepts:

​

●Cause and Effect

● Patterns

​

​

Standards

Standards for Mathematical Practices (MP)

1. Make sense of problems and persevere in solving them.

2. Reason abstractly and quantitatively.

3. Construct viable arguments and critique the reasoning of others.

4. Model with mathematics.

5. Use appropriate tools strategically.

6. Attend to precision.

7. Look for and make use of structure.

8. Look for and express regularity in repeated reasoning.

​

Objectives:

• I can explain if Earth’s gravity affects objects of different masses.
• I can write a hypothesis using “if”, “then” and “because” statement.
• I can weigh and calculate the mass of the nuts and bolt.
• I can calculate the mean of three consecutive trials.
• I can create a bar graph with a title and label its axis.
• I can analyze and interpret my data and conclude if the gravity on Earth is affected by different masses.

Agenda

Day 1

• Review how gravity affects objects on Earth and its gravitational pull on Earth (9.807 m/s²).
• Have student predict if different masses hit the ground at the same time (most students will say that heavier objects hit the ground first).
• Review the “Free Fall Lab” procedures (see slide 8) with students and have students write their hypothesis.
• Have students calculate the mass for each scenario (ex. 1 bolt and 1 nut etc) and place on the “Free Fall Lab”.
• Have students time how long the nuts and bolt hit the ground and write the data on their “Free Fall Lab”.

Day 2

• Students will finish obtaining their data, if they didn’t complete it the day before.
• Students will calculate the mean of each scenario (ex. 1 bolt and 1 nut). See the “Free Fall Lab” on slide 8.
• Students will create a bar graph and answer the analysis question on the “Free Fall Lab”.

Intro/Driving Question/Opening

​

​

If given different objects with different masses, which object will hit the ground first? The heavier object? The lighter object? Or would they hit the floor at the same time? Explain your answer.

In today’s lab, you will be using 1 bolt and different amount of nuts to test if the mass affects how fast the bolt and nut(s) will hit the floor.

Hands-on Activity Instructions

• One student holds the meter stick. The second student holds the bolt/nut and lets it go. The third student (not seen in picture) is timing how fast it hits the ground. The fourth student is recording the time on the “Free Fall Lab” on document.

​

• This is repeated three times for each scenario (1 nut, 2 nuts, 4 nuts, 6 nuts). See slide 9.

​

​

Let’s examine how the lack of air resistance affects falling objects. Click on link to watch video.

https://www.youtube.com/watch?v=E43-CfukEgs

Assessment

1. Think about your data, explain if there is a relationship between the mass of an object and the time it took to hit the floor? Use your data as evidence when explaining your answer.
2. Explain what causes objects to hit the floor at different times on Earth. Provide an example when explaining your answer (hint: think air resistance).
3. How would you design an experiment to test you answer to #2 above.

​

Differentiation

One way to differentiate is for the teacher to perform this lab as a class. Students will still be grouped but instead of having students obtain their data independently, the teacher will have students come to the front of the class to obtain their data as a class. If the class has more than 5 groups (1 nut, 2 nuts, 4 nuts, and 5 nuts), teacher can add additional nuts to the lab.

Remediation

Extension/Enrichment

• As an extension, the class will gather all the groups’ data and place it on a data table.
• Students will calculate the mean for each group.
• Students will see that the mean is very similar between the bolt with one nut and the one bolt with 6 nuts. See sample data on slide 13.
• Students can then make a bar graph with this data and discuss their findings.

Example of the extension