Energy, Machines, and Motion

Part One: Energy

Students are introduced to the scientific meaning of work. Students build a sled and try to lift it with the optimum conditions of the motor.

Focus Question: What is the relationship between forces applied and the work that is done?

1. Content Standards

EALR 2: Inquiry
Core Content: Questioning and Investigating

6-8 INQC Collecting, analyzing, and displaying data are essential aspects of all investigations.

6-8 INCF It is important to distinguish between the results of a particular investigation and general conclusions drawn from these results.

EALR 3: Application
Core Content: Science, Technology, and Solving Problems

6-8APPH People in all cultures have made and continue to make contributions to society through science and technology.

EALR 4: Physical Science
Core Content: Balanced and Unbalanced Forces

6-8 PS1C Unbalanced forces will cause changes in the speed or direction of an object’s motion.

2. Concepts

Students define “work” scientifically as the product of a force times the distance over which that force was applied.
Students learn the metric unit of measure for work is the newton-meter, which is also called the joule.
Students compare the force of three batteries in series around the nail compared to the force needed to lift a sled.

3. Lesson Set-Up and Management

Materials:

Students will be making a sled out of 14 washers and K’NEX™ pieces as outlined in the teacher’s edition. Place those pieces into a plastic bag so students can quickly build their sleds. You may consider making a list of materials for the sled to be laminated and inserted into the plastic bag so students can easily check if a piece is missing.
Have a place where missing or extra K’NEX™ pieces can be accessed. Consider having a plastic bin for “spare” or missing parts.
Students will add 14 washers to their sled. This is not clear in the student directions and is only outlined in the materials list.
Make copies of lesson sheets 8.1a, 8.1b and 8.2a prior to the lesson.
Students will also need to be able to access data from Lesson 6.1 where they collected the force for moving a block across different surface types. You may want to have the force of this lesson available for students.
Make sure batteries are completely charged for Lesson 8.2.

Student Management - Lesson 8.1:

As a group of four, students will discuss the meaning of work and make a list of examples of what they consider to be work. Students tend to consider work as something physical or hard. By having students write out their definitions of work you are helping them overcome this misconception of this term.
Students will then read a selection on scientific view of work; students will then go back to their list to identify components of their list that would actually be considered work.
Students are asked in the Getting Started to determine the amount of work it will need to move a sled. Have students write out the equations so they can use this as a reference in future parts of this lesson and other lessons.

Student Management - Lesson 8.1:

Students mark a vertical distance of 10 cm with tape on their peg boards.
Have students wrap the string around the nail so the paper clip hangs just below the bottom mark. They are only observing if the motor can lift the six washers.
Student Sheet 8.2 can be confusing to students. You may want to work through this record sheet with your students.
Students calculate the amount of work needed to lift the sled 10cm, students then predict what should happen to the sled, will it be able to lift with the motor? Make sure students are focused on the data to make an informed prediction.

4. Teacher Tips:

Lesson 8.1

In Lesson 8.1 have students come up with a list of what they consider to be work along with a definition of work.
Go through the reading together. The concepts in this reading are vital for this lesson and the next several lessons.
Sample data in the Teacher’s Edition may include an error depending on which edition you have. The Effort Force of the different surfaces is correct in Lesson 6.

Lesson 8.2

Student Sheet 8.1b is a good assessment regarding if students understand how to calculate work.
In Lesson 8.2 students calculate how much work the motor should be able to do and compare that with lifting 6 washers and the newly constructed sled containing 14 washers.
The motor is not designed to lift such a heavy load and will not lift the sled. You will want to spend time connecting the math of how much work the motor can do against the work needed to lift the sled.
When the sled doesn’t lift the sled students must determine that there is no work done because there is no distance traveled.
This concept will be important in Part 2 of Energy, Machines, and Motion when students use a simple machine to reduce the effort force and increase the effort distance to move the sled. The assessment at the end of the second part will have the students use both the motor and a simple machine to move the sled a vertical distance of 10cm.
Keep sleds intact for Lesson 11, 12, 13, and 16.

5. Literacy Support

Writing Support:

Students brainstorm a list of what they consider to be work before given the scientific definition. You may also want to include having students write why they consider the following work. This will help them confront a common misconception that work is hard or physical.
Have students write the formula for work in their notebooks. Make sure that they also include the unit of measurement. This will be a formula students can refer back to if they need a reminder.
Student record sheets can be pasted into student notebooks. Consider trimming margins so that they can be glued directly into the notebook.

Reading Support:

“The Meaning of Work” introduces the scientific meaning of work and how it is calculated. Students will learn the unit of measurement for work is called newton-meters or joules.
There are two readings to support what students have learned after completing Lesson 8.1 and Lesson 8.2.
- “MEASURING UP” gives a historical perspective in how units of measurement were named after scientists
- “Klamath Falls—A Real Hot Spot” describes how thermal energy put to use in this city.

Math Support:

It is essential that students convert centimeters to its meter equivalency, 10 cm is equal to 0.1 meters, 24 cm is equal to 0.24 m.
Students make predictions based on looking at the potential force the motor can exert and the force needed to lift the sled.
Students calculate the work needed to move a block of wood over different surfaces. Make sure that students understand the differences in the calculations. You may want to consider rounding calculations to the nearest hundredth.
Some students are still not confident with the differences in numbers with decimals. Check for understanding of student results.

Last updated 09/09/2009