Last Lesson
In our last unit, we learned the basics of programming. Now, we need to learn some very basic elements about what machines do. We will then learn to build different mechanisms while programming them.
Evaluation
You will be evaluated for this lesson based on your ability to:
- define the motion types.
- define power and input reversibility.
- determine the motion types and reversibilities for mechanisms through analysis.
Demonstrations
Create a section for this lesson in your Notebooks. You will read through the materials below and watch the example videos. As you do, remember to record the critical information as notes in your Notebook.
In all machines, force and energy are being used. Most machines provide an advantage by changing the input energy in some way: direction, location, speed, distance and force can all be affected.
In general, most machines humans use depend on the same sort of input: rotation. Something spins, and then that spin can be used to cause other kinds of motion. In general, the OUTPUT (the resulting motion) or the INPUT (the starting motion) can be categorized as belonging to one of these three:
In all machines, force and energy are being used. Most machines provide an advantage by changing the input energy in some way: direction, location, speed, distance and force can all be affected.
In general, most machines humans use depend on the same sort of input: rotation. Something spins, and then that spin can be used to cause other kinds of motion. In general, the OUTPUT (the resulting motion) or the INPUT (the starting motion) can be categorized as belonging to one of these three:
- Rotary – The output spins in a single direction. Think of machines like cars, where the crankshaft in the engine spins, causing the wheels on the car to spin. That is an example of rotary motion. As long as the input rotation stays the same and the gears are not changed, the rotation will always be in the same direction. Watch the quick video example below, and then move on.
2. Reciprocal – The output moves back and forth, either through an arc or in a straight line. The pistons in a car engine are a reciprocating mechanism because they slide back and forth, even though the engine is always turning in one direction. When motion is through an arc, it is called oscillation.
3. Linear – The output moves in a straight line AS LONG AS THE INPUT DOESN’T CHANGE. In linear movement, if we reverse the input motion, then we can reverse the direction. This is NOT the same as reciprocating motion, even though it looks similar. A car moving along the road because of the rotation of its wheels is an example of linear motion. As long as the wheels keep rotating in the same direction (input is the same) then the car will keep moving in the same direction (output direction.) Think of a car. As long as the wheels turn the direction of motion will be "forward". If we want to reverse this, we need to reverse the rotation of the wheels.
Reversibility refers to whether moving either part will work to
We Do It
Let's discuss these motion types! We'll do a quick Timed Pair Share, and then talk as a class.
You Do It Together
Create a section in your Notebook for Notes, and record the questions you are supposed to answer about the following machines. With your shoulder partner, determine the answers for all the following machines. Record your answers in your notebooks.
- What kind of input motion does it have?
- Can moving the output mechanism completely move the input mechanism? Is it power reversible?
- Does the machine work when you reverse the rotation of the input? Is it input reversible?
- What type of output motion does it make?
You Reflect
- Log into OTUS.
- Take the Mechanical Motion Formative Quiz.
- Take the Mechanical Motion Formative RWE, and record your LENS reflection.
Extension
If you complete the work before your peers, you must:
- Identify a relatively simple machine.
- Identify the motion types and reversibilities for that machine.
- Submit the analysis to your instructor as a shared google doc.