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Systems in Action

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Phil Doyle

on 23 February 2013

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Transcript of Systems in Action

Input 1 Why Use Machines?- A machine is any mechanical system that reduces the force required to accomplish a task. Machines are designed to help make things easier for people to do. They meet a specific need or perform a task. Input 3 A simple machine is a device, composed of only one or two parts, that requires a simple force to work There are six simple machines: the inclined plane, the wedge, the screw, the lever, the wheel and axle(gears), and the pulley. A complex machine is made by combining two or more simple machines. Input 2 What to Study Force A force is a push or pull, that causes a change in the motion of an object.

All forces have two components - magnitude and direction.

Magnitude is a measure how strong the force is.

Direction refers to which way the force is pulling or pushing.
The unit to measure force is the newton (N), named after Sir Isaac Newton. The unit test will cover everything we have covered in the unit (make sure you have all of your notes and lab activities).
You will need to know:
-how machines can make work easier
-the different simple machines, how they are categorized, and examples of each
-the different classes of levers and types of pulleys
-how to calculate WORK and MECHANICAL ADVANTAGE A machine can make work easier in the following ways:
1. Transform the energy
2. Transfer forces from one place to another
3. Change the direction of the force
4. Change the magnitude of a force
5. Increase or decrease speed Systems in Action
Unit Review Simple machines can be categorized
into those that are related to the
inclined plane and those related to the

Related to the Inclined Plane:
- the wedge
- the screw

Related to the Lever:
- the wheel and axle
- the pulley What is WORK? The scientific definition of work is: using a force to move an object a distance (when both the force and the motion of the object are in the same direction).
work = force applied (in newtons) x distance moved (in metres) OR W = F x d
The amount of work done is measured in units called joules (J), named after the English scientist James Prescott Joule. Force is always expressed in Newtons (N). Distance is always measured in metres. If the unit is not in metres, it must be converted into metres. Work Mechanical Advantage (MA) is the ratio of the output force
to the input force (for example, the output force divided by the input force).
Mechanical advantage (MA) has no units, it is simply a comparison or ratio.
Machines with a mechanical advantage greater than 1 generally makes the task easier and faster to accomplish.
It is possible to have a mechanical advantage of less than 1. This happens when the input force is greater than the output force.
Calculating Mechanical Advantage
Ideal MA: Can be calculated two different ways. You can use the effort arm length and load arm length (in levers); effort arm length divided by load arm length. You can also use the input and output distances (pulleys); input distance divided by output distance
Actual MA: Is calculated when you know the actual forces.
It is calculated using the input (effort) force and output
(load) force values. Formula: output force divided by
input force MA Don't understand something? Don't wait to the last minute, come for extra help ASAP!
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