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The Ups and Downs of Weight and Mass (Grades 7-9)

Master Teacher

Karenanne Koenig

Overview

This lesson will allow students to explore the concept of mass, and how it differs from weight. Students will determine their weight change as they ride up and down on an elevator.

SC Science Standards Met

Inquiry: A. Abilities Necessary to Do Scientific Inquiry—observe, observe patterns of objects and events, classify, arrange data in sequential order, measure, select and use appropriate tools

Infer: make inferences based on data

Predict: predict the results of actions based on patterns in data

Use technology and Mathematics To Improve Investigations and Designs

Earth: Unit of study: Earth and Space Systems: 8. Unbalanced forces will cause a change in the speed or direction of an object's motion c. Describe an object in free fall.

Learning Objectives

Students will be able to:

define weight
differentiate between mass and weight
identify the units for force and mass
record the changes in their weight as the elevator moves
graph the collected data

Materials

For each partnership:

bathroom scale
stopwatch
Weight Watching Woes Experiment
pencil

ITV Series

Eureka, Lesson #7, "Mass"

Previewing Activity

Provide students with a bathroom scale and a newton and dyne scale. Distribute Activity Sheet 1 and ask students to list the attributes of both scales. Mindmap the students' collective attributes. Ask them to compare the two scales. Record the responses on the board.

Focus for Viewing

In order to provide students with specific tasks during the viewing of the video segment, hand out Activity Sheet 2, "Focus for Viewing." The sheet requires students to define mass and weight, differentiate between mass and weight, state the origin of the word gravity, and list one item that has a mass of 100g and one item that measures 1 newton of force.

Viewing Activity

Start the video at the segment entitled "Weight vs. Mass." Stop the video when the narrator states, "All of these have a mass of about 100 grams." Direct students to fill in their Focus for Viewing Sheets (FFVS).

Restart the tape once students have completed their task. Stop when the narrator states, "What you weigh merely means what force of gravity is pulling you down to earth." Direct students to fill out the FFVS.

Resume playing the tape until you hear the narrator say, "...which is simply Latin for weight." Direct students to fill out their FFVS.

Start the tape when the students have completed their task. Stop when the narrator says, "In physics, kg measures mass on a balance scale." Direct students to fill in their FFVS.

Resume playing the tape until you hear, "But your weight is always measured in newtons." Direct students to fill in the FFVS.

Play the tape again until you hear the narrator state, "Wherever you go in the universe your mass stays the same, only your weight changes." Direct students to fill in their FFVS.

Post-Viewing Activities

1. Review the Focus for Viewing Sheet

Question: List an object that has the mass of 1 gram and the force of 1 newton.

Answer: apple, two golf balls, D battery

Question: What is weight?
Answer: Weight is the force of gravity pulling you down to earth.

Question: What is the origin of the word gravity and what does it mean?
Answer: Gravitas, from the Latin word meaning weight.

Question: What unit measures mass?
Answer: kg.

Question: What unit measures weight on earth?
Answer: Newtons.

Question: What is the difference between weight and mass?
Answer: Mass doesn't change wherever you go in the universe, weight changes with the gravitational force.

2. Allow students to perform the Weight Watching Woes Experiment (Activity Sheet 3).
3. After students have completed the Weight Watching Woes Experiment, direct them to enter their results into a data table that includes the results of other classmates.

Action Plan

1. Assign students to further research - The Weight Equation

2. Assign students to further research - Forces on a Falling Object

3. Provide students with ropes and direct them to build a model of an elevator.

Extensions

1. Technology: As an extension of the Weight Watching Woes Experiment, direct students to explore the technology of how an elevator works.

2. Writing: Instruct students to write thank-you notes to the community members who were kind enough to let the class use their elevator. Publish the letters on the team page or on the school's Web page.

3. Take pictures of the students performing the Weight Watching Woes Experiment and publish them on the Web page.

Activity Sheets (PDF)