Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Define a simple mechanism and identify examples.
• Explain how a mechanism can change the size or direction of a force.
• Calculate the mechanical advantage of a simple lever.
• Describe the relationship between effort, load, and mechanical advantage.
• Identify simple mechanisms in common household objects.

Lesson summary

This week, we begin our exciting journey into the world of Systems and Control, specifically focusing on Simple Mechanisms and Mechanical Advantage. Understanding how machines work is crucial, whether you're fixing a bicycle in your backyard, designing a new tool, or even understanding how the gears in a car work. Simple mechanisms are the building blocks of all machines, from the simplest lever to the most complex robot. By understanding how these mechanisms work, you'll gain a practical understanding of how forces can be manipulated to make our lives easier.

Lesson notes

Let's break down the core concepts of simple mechanisms and mechanical advantage: Simple Mechanism: A simple mechanism is a basic device that changes the direction or magnitude of a force. It takes an input force (effort) and transforms it into an output force (load). Common examples include levers, gears, pulleys, inclined planes, wedges, and screws. This week, we'll focus primarily on levers.

Effort (Force Input): The force you apply to the mechanism. Think of pushing down on a lever or pulling a rope.

Load (Force Output): The force the mechanism applies to overcome resistance. Think of lifting a heavy rock with the lever or lifting a bucket of water with a pulley.

Mechanical Advantage (MA): Mechanical advantage is the ratio of the load force to the effort force. It tells us how much easier a mechanism makes work. It's a number (with no units) that indicates how many times the mechanism multiplies your effort.

Formula: MA = Load / Effort Lever: A lever is a rigid bar that pivots around a fixed point called a fulcrum. Levers are used to multiply force or distance. There are three classes of levers, distinguished by the relative positions of the fulcrum, load, and effort: Class 1 Lever: The fulcrum is between the effort and the load (e.g., a seesaw, crowbar).

Class 2 Lever: The load is between the fulcrum and the effort (e.g., a wheelbarrow, bottle opener).

Class 3 Lever: The effort is between the fulcrum and the load (e.g., tweezers, fishing rod).

Leverage and Distance: The mechanical advantage of a lever is determined by the distances between the fulcrum and the points where the effort and load are applied. The further the effort is from the fulcrum compared to the load, the greater the mechanical advantage. MA = Distance from Effort to Fulcrum / Distance from Load to Fulcrum