Lesson An Introduction to Inclined Planes

Learning Objectives

After this lesson, students should be able to:

• Identify inclined planes as a type of simple machine.
• Identify at least one way in which simple machines make a specific task easier to accomplish.
• Explain that the purpose of simple machines and tools is to make a specific type of work or task easier to do.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Introduction/Motivation

How did you get to school today? Why did you take the bus/car? Would you rather have walked that long distance? So using a car/bus, did you get to school faster and easier than if you had walked? Well this is because a car/bus is an example of a very complex tool that people use to make traveling easier! Can anyone else name some simple tools that you might see around your house? (Possible example answers: Hammer, screwdriver, kitchen appliance, etc.) Very good! And what does this tool do? Can anyone tell me why we might need to use tools like this hammer? Would you be able to take this nail and push it through a piece of wood with just your hands? No? This is because people use tools to help them do things that they cannot do on their own. Tools are used to make work easier. Imagine if you invented a homework machine!

Today we will explore a simple tool that you might not know much about. It's called an inclined plane. Does anyone know what inclined means? Inclined is when something is tilted, so that part of it is touching a lower point in space than the other. A plane is anything that is large and flat, like a piece of paper or wood or a football field. So now that you know what inclined and plane mean, what is an inclined plane? An inclined plane is a large flat object that is tilted so that it goes from a lower point in space to a higher one (show an example using a flat piece of wood or cardboard). What might this tool be used for? Let's say you're a professional skateboarder and you want to try out a cool trick, but what do you need? You need some AIR! What does a skateboarder use to get in the air? That's right! A ramp! But what is a ramp? (Draw one on the classroom board). A ramp is just a flat piece of wood that is tilted upwards, so that a skateboarder can get from the ground to up in the air and pull off his trick! This makes a ramp an inclined plane! Who else might use an inclined plane besides a skateboarder? Let's say you are an engineer building a road from here to California (draw a general map on board), but what is in your way? (Answer: Rocky Mountains.) That's right, these gigantic Rocky Mountains are blocking the road! How do engineers build roads over mountains? They use hills! Whenever you drive up a hill on the road, you're driving up an inclined plane!

Remember how we said that tools are used to make work easier? Now that we know an inclined plane can be used to move something (car, skateboarder, etc.) from a low point to a high point, let's find out why inclined planes make work easier. Refer to the associated activity The Benefits of Inclined Planes: Heave Ho! to help illustrate how inclined planes can be of assistance by conducting a hands-on experiment.

Lesson Background and Concepts for Teachers

Teachers should be familiar with the role inclined planes play as simple machines and some examples of their real-world applications for use during the lesson. Inclined planes serve as tools that reduce the work necessary to transfer objects to different vertical heights. As students discover in the lesson, the actual weight lifted up an inclined plane turns out to be significantly less than the weight that would be lifted if the object were lifted straight up into the air. Inclined planes find their way into roadway construction, bike and skateboard ramps, wheelchair access, etc.

Many tasks that we undertake in everyday life require the use of tools. These tools can be as simple as forks and spoons to help us eat or as complicated as cars and airplanes to help us travel around the world. But why use these tools? Tools and machines that humans design and use are meant to make certain tasks easier, and move other tasks into the realm of possibility. One category of everyday tools that many students are familiar with is simple machines. This category consists of levers, inclined planes and pulleys. These are very basic tools with practical, everyday applications. The one investigated in this lesson is inclined planes.

The function of the inclined plane is to reduce the effective weight of the object. An object being pulled up an inclined plane requires less force than an object hoisted vertically. When an object is pulled up an inclined plane a significant portion of the total weight of the object is supported by the ramp and the rest supported by the person pulling. How much of this weight is supported by the ramp and how much must be pulled by the person depends on the angle of inclination of the ramp. This concept is illustrated in the diagram below in which W represents the total weight of the object, W_y represents the portion of the weight supported by the ramp and W_x represents the portion of the weight "felt" or actually pulled by the individual.

In contrast, when an object is lifted vertically, the extra support of the ramp does not exist and the entire weight of the object is instead supported by the person doing the lifting. This fact of physics allows inclined planes to make the task of changing the vertical height of an object, say a car using an inclined road to drive up a mountain, use less work than if it were instead lifted straight up, say a car being hoisted over the mountain, which just isn't practical.

Associated Activities

• The Benefits of Inclined Planes: Heave Ho! - Students conduct a hands-on experiment to investigate exactly how inclined planes make work easier.

  Watch this activity on YouTube

Lesson Closure

So what are some things we learned about tools today? We learned that tools are used to make work easier. What were some of the tools around the house that we named before? What kinds of work to they make easier? How? Can someone define an inclined plane for me? What is it used for? Can anyone name an example of an inclined plane? How do they make work easier?

Engineers use inclined planes all the time, whether to construct roads, skateboarding ramps, handicap access, sidewalk ramps, etc. Next time you are driving over some big mountains, think about the reasons why engineers decided to use the inclined plane to get your car over the mountain. Would you have wanted to have walked?

Vocabulary/Definitions

angle of inclination: The angle that the inclined surface makes with the horizontal ground. The greater the angle, the greater the effective weight of the object, but the shorter the distance to the top of the inclined surface.

effective weight: Weight "perceived" or "felt" by a person pulling an object up an inclined plane; defined to be less than the actual weight of the object.

inclined: A slanted surface, a surface deviating from horizontal.

inclined plane: A simple machine without moving parts, used to increase the height of an object. Made using a flat, slanted surface, such as a ramp.

Assessment

Post-Introduction Assessment: As a class, go through the questions on the Pre-Activity Worksheet. Guide the answers of the class to formulate a correct mind-frame before the experiment.

Post-Lesson Assessment: Use the Experiment Worksheet and the concluding Design Worksheet from the associated activity, The Benefits of Inclined Planes: Heave Ho!, as tools to evaluate student understanding.

Copyright

Contributors

Supporting Program

Acknowledgements

This content was developed by the MUSIC (Math Understanding through Science Integrated with Curriculum) Program in the Pratt School of Engineering at Duke University under National Science Foundation GK-12 grant no. DGE 0338262. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.