Overview
We are surrounded by the use of machines to construct and maintain buildings and roads. We see massive objects raised and lowered into position. Large machines can literally move mountains over a period of time. As we maintain our homes, make repairs, move furniture, clean and pick up our "stuff" we utilize simple machines. Some of these simple machines are actually part of our physical make up.
These labs will help students recognize simple machines as they are used by them and around them. They will be able to calculate the amount of work done and utilize simple machines to accomplish work more easily.
To more clearly view the work of simple machines without the initial complication of combining them in complex machines, we have set these activities in a situation where simple machines were used to accomplish enormous amounts of work. The grouping of the simple machines within each lesson is done to support their sequential use in this setting. Full understanding of the wedge in Activity 1 will be accomplished by referral back following the introduction of the inclined plane in Activity 2.
To complete the lessons, each student will need a printed lab packet for 3 seperate activities. The lab packets are on this page for download and printing. Students are encouraged to work in pairs and prompted to discuss their ideas throughout the lessons. The lab packet can be turned in for homework or kept for future reference.
Lesson Outline
Introduction
Our characters, Harry and Pic, have accepted a challenge to create a city constructed of large stones using only simple and complex machines. Students are introduced to the concept Mechanical Advantage and charged with their task.
Activity One: Simple Machines - The Wedge and Lever
- 1a. Students will investigate the use of the wedge to accomplish work in a direction different from the force initially applied, with particular attention to the selection of the most appropriately shaped wedge.
- 1b. Students will collect data as they exert force on a lever through varying distances to accomplish a desired amount of work. They will calculate mechanical advantage.
Activity Two: Simple Machines - The Inclined Plane and Pulley
- 2a. Students will investigate the inclined plane as a simple machine while attempting to transfer a large stone to the top of a construction sight.
- 2b. Students will collect data as they adjust the length of the inclined plane. They will compare work input and the relationship of inclined plane length to the work input.
- 2c. Students will investigate the connection between the inclined plane and the wedge.
- 2d. Students will investigate the use of a pulley system to change direction of force and input force required by increasing the number of supporting ropes.
- 2e. Students will collect data as they test various pulley systems and by graphing the data, they will describe the relationship between input force and number of supporting ropes.
- 2f. Students will evaluate the mechanical advantage gained by combining simple machines.
Activity Three: Simple Machines - The Wheel and Axle and Screw
- 3a. Students utilize the screw to lift a stone slab used as an irrigation gate. The screw is introduced as a special inclined plane.
- 3b. Thread density is adjusted and data is collected and graphed to compare the advantage gained by varying thread density.
- 3c. Students will adjust the radius of a wheel to investigate the changes in effort applied and distance of effort movement.
- 3d. Students will investigate the advantage of combining the wheel and axle with the screw.
Science
Most modern machines are combinations of the six simple machines. These devices rely on a few simple principles. Work is defined as the movement of a force through a distance. The simple machine can not reduce the amount of work needed to complete a task, however, it can reduce the effort needed from the user.
- Work = F x D
- F(resistance)D(resistance) = F(effort)D(effort)
The Force applied (FE) times the Distance the effort must move (DE) equals the work done by the effort force.
The Force of the resistance (FR) (frequently the weight of the object to be moved) times the distance the resistance moves (DR) is the work done.
If (FR) > (FE), then (DR) < (DE)
By increasing the distance the effort moves, the amount of effort can be reduced.
Increasing the effort force applied reduces the distance it must move to accomplish the same amount of work.
A third advantage to be gained by using a simple machine is changing the direction of the force.
These activities use SI units (the metric system).
- The SI unit for weight and other forces is the Newton (N).
(4.45N = 1 pound) - The SI unit for the distance or length is the meter (m).
(1 meter = 3.28 feet, 2.54 cm = 1 inch)
Standards
Utah Science Core: Eighth Grade
Students will understand the relationships among energy, force, and motion.
Objective 3
Investigate the application of forces that act on objects, and the resulting motion.
a. Calculate the mechanical advantage created by a lever.
b. Engineer a device that uses levers or inclined planes to create a mechanical advantage.
c. Engineer a device that uses friction to control the motion of an object.
d. Design and build a complex machine capable of doing a specified task.
e. Investigate the principles used to engineer changes in forces and motion.
Benchmarks 2061 - Grades 6-8
4. The physical setting
4F Motion:
- An unbalanced force acting on an object changes its speed or direction of motion or both. If the force acts toward a single center, the objects path may curve into an orbit around the center.
9. The Mathematical World
9B Symbolic Relationships:
- Mathematical statements can be used to describe how one quantity changes when another changes. Rates of change can be computed from differences in magnitudes and vice versa.
- Graphs can show a variety of possible relationships between two variables. As one variable increases uniformly, the other may do one of the following: increase or decrease steadily, increase or decrease faster and faster, get closer and closer to some limiting value, reach some intermediate maximum or minimum, alternately increase and decrease indefinitely, increase or decrease in steps, or do something different from any of these.
9C Shapes:
- The graphic display of numbers may help to show patterns such as trends, varying rates of change, gaps or clusters. Such patterns sometimes can be used to make predictions about phenomena being graphed.
12. Habits of Mind
12D Communication skills:
- Organize information in simple tables and graphs and identify relationships they reveal.
National Science Education Standard grades 5-8
B Physical Science
- Motions and Forces
A Scientific Inquiry
- Use appropriate tools and techniques to gather, analyze, and interpret data.
- Use mathematics in all aspects of science inquiry.
- Develop descriptions, explanations, predictions, and models using evidence.
Intended Learning Outcomes
1. Use Basic Science Process Skills
- a. Make observations and measurements (uses instruments as appropriate).
2. Use Integrated Science Process Skills
- a. Identify variables and describe relationships between them. e. Analyze data and draw warranted inferences.
- g. Construct models and simulations to describe and explain natural phenomena.
4. Demonstrate Awareness of the Social and Historical Aspects of Science
- d.Recognize the personal relevance of science in daily life.
5. Understand Science Concepts, Principles, and Systems
- a. Know science terminology appropriate to grade level.
- e. Solve problems by applying science principles and procedures.
6. Communicate Effectively Using Science Language and Reasoning
- a. Use the language and concepts of science as a means of thinking and communicating.
Oral and written discourse is important. It focuses the attention of students on how they know what they know and how their knowledge connects to larger ideas. In these lessons, students are encouraged to express their ideas in complete sentences rather than single word or short phrases. This practice helps them to express underlying ideas completely and to reinforce their understanding of the concepts.
Small group collaboration is part of scientific inquiry. Throughout the lessons pairs or small groups of students should work together to brainstorm ideas/questions, share data, and engage with their classmates in explaining, clarifying, and justifying what they have learned.
Contacts
Technical consultation and assistance is freely available to teachers and schools interested in using the ASPIRE website, on-line labs, and curriculum materials. In time, resources will be made available to assist schools lacking the computer technology required to access the labs. For technical assistance and resource information, please contact julie@cosmic.utah.edu