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Machines simple and complex work and mechanical advantage

Machines notes with mechanical advantage science physical science

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MACHINES
MACHINES • The purpose of a machine is to make work easier. • This is done in 3 ways: 1. Decreasing Effort Force- the force that YOU must apply Ex. Using a screwdriver 2. Increasing the distance over which the force is applied Ex. Ramp 3. Changing the direction of the applied force Ex. Pulley
MACHINES •There are 2 classifications of machines that we will be discussing: • Simple Machines • Complex Machines
SIMPLE MACHINES • A simple machine can do work in 1 motion/movement. • Simple machines do NOT change the amount of work done but they reduce the effort force that is required to do the work.
There are six types of simple machines: 1. Inclined Plane 2. Wedge 3. Screw 4. Wheel and Axle 5. Lever 6. Pulley Inclined Plane Wedge Screw Wheel & Axle Lever Pulley SIMPLE MACHINES
• An inclined plane is a device that increases the distance by which the effort force is applied • An inclined plane makes it easier to raise or lower heavy objects. • Examples: Slide, Stairs, Ramps INCLINED PLANE INCREASES DISTANCE
• As the angle of the inclined plane decreases, the force required to raise the object decreases. • Although the inclined plane requires a smaller force to raise the object, it requires that the force be applied over a greater distance. The increase in distance is proportional to the decrease in force. A greater force is needed to raise an object using this inclined plane, but the force is applied over a smaller distance A smaller force is needed because the angle is smaller, but the force must be applied over a greater distance INCLINED PLANE
• A wedge is a modified inclined plane. Therefore, wedges also make work easier by increasing the distance over which a force is applied. • The sides of a wedge come to a point so that the wedge can be driven into an object. • A wedge is used to split objects or hold objects in place. • Examples: Ax, Nail, Shovel, Knife WEDGE
• Not only does the wedge increase the distance over which a force is applied, but it can also make work easier by changing the direction of a force so to separate objects. • When a person uses a wedge, he applies a downward force. In turn, the wedge applies a horizontal force to an object. The horizontal force splits the object into two parts. WEDGE
• A screw is an inclined plane wrapped around a cylinder. This creates threads. • Since the screw is a form of an inclined plane, it also makes work easier by increasing the distance over which the force is applied. • A screw is used to connect objects together. • Examples: Screw, Jar lid, Bottle opener SCREW
• A screw can also make work easier by changing the direction of an applied force. You apply a rotational force to vertically drive a screw into an object. • IMPORTANT: The more threads on a screw, the less force needed to drive the screw into an object. However, you must rotate the screw more times to drive it into an object. SCREW
• A wheel and axle is simple machine that consists of a wheel attached to a rod (known as an axle). • The W&A makes work easier by decreasing the effort force applied AND increasing the distance that the force is applied over. • A wheel and axle is used to lift or move objects with less frictional force. • Example: Wagon wheels, Bike wheels, Car tires WHEEL & AXLE
• A wheel and axel decreases the force you must apply to move an object across a distance but you must apply that force over a greater distance. • The wheel and axle rotate together. If force is applied to the wheel, the axle turns. If force is applied to the axle, the wheel turns. • IMPORTANT: The larger the radius of the wheel, the easier it is to use the wheel and axle to do work. WHEEL & AXLE
• A lever is a board or bar that sits on a fixed point called a fulcrum. The level pivots or moves on the fulcrum. • A lever makes it easier to lift and lower objects by decreasing the effort force. • Examples: Hammer, Scissors, Rake, using a screwdriver to open a paint can. • We will discuss the 3 types of levers a little later in the lesson. LEVER
• A lever can ALSO change the direction of a force. If you apply a downward force to a lever, you can raise an object. Fulcrum Direction of Effort Force Direction of Resistance Force (AKA: LOAD) LEVER
• A pulley is a wheel with a groove around its outside edge. The groove is for a rope or belt that can move around the pulley. • A pulley makes work easier by changing the direction of the applied force. • A pulley is used to lift or lower objects. • Examples: Water well, Window shade, Crane PULLEY
• A pulley can also decrease the force needed to raise an object. In doing so, the force must be applied over a greater distance. Pull down... to lift an object. PULLEY
• When you use a simple machine, you apply a force to that machine. This force is called input force or effort force. • The effort force causes the machine to perform work. The work performed by the machine is called output force, resistance force or load. • Using a simple machine gives its user an “advantage.” This is known as Mechanical Advantage and is the ratio of the force produced by a machine to the force applied to it, used in assessing the performance of a machine. Effort Force- the force applied by the person Resistance Force- the force applied by the machine MECHANICAL ADVANTAGE
• A lever can increase mechanical advantage. • The further the input force (effort) is from the fulcrum, the greater the output force (load) and thus, the greater the mechanical advantage of the lever. • If the input force is closer to the fulcrum that the load, then the lever does not provide mechanical advantage. More mechanical advantage EFFORT FORCE RESISTANCE FORCE Less mechanical advantage MECHANICAL ADVANTAGE FE FR EFFORT FORCE RESISTANCE FORCE FE FR
• There are three classes of levers • 1st Class: fulcrum in middle • 2nd Class: load/resistance force in middle • 3rd Class: effort force in middle • With each type of lever, the location of the effort (where the input force is applied), the fulcrum and the load (where the output force of the lever is applied) changes. CLASSES OF LEVERS
Example of First Class Lever: FULCRUM EFFORT FORCE RESISTANCE FORCE To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE
What is the MA of this machine? EFFORT FORCE= 6 N RESISTANCE FORCE= 12 N To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE MA= 12 N 6 N MA= 2
Example of Second Class Lever: To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE EFFORT FORCE RESISTANCE FORCE FULCRUM
What is the MA of this machine? To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE EFFORT FORCE= 90 N RESISTANCE FORCE= 270 N FULCRUM MA= 270 N 90 N MA= 3
Example of Third Class Lever: FULCRUM EFFORT FORCE RESISTANCE FORCE To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE
What is the MA of this machine? EFFORT FORCE= 2.5 N RESISTANCE FORCE= 5 N To calculate the Mechanical Advantage of a lever you must use the following formula: MA= FR FE MA= 5 N 2.5 N MA= 2
100 N 100 N What is the MA of this machine? To calculate the Mechanical Advantage of a pulley you must use one of these two formulas: MA= FR FE MA= DE DR Force applied by the machine/load Force applied by the person Distance over which the effort force is applied Distance over which the load is working against the effort force Since we are given FORCES, we will use this formula to find MA
100 N 100 N What is the MA of this machine? MA= FR FE MA= 100 N 100 N MA= 1
1 0 m 10 m What is the MA of this machine? To calculate the Mechanical Advantage of a pulley you must use one of these two formulas: MA= FR FE MA= DE DR Force applied by the machine/load Force applied by the person Distance over which the effort force is applied Distance over which the load is working against the effort force Since we are given DISTANCES, we will use this formula to find MA
1 0 m 10 m What is the MA of this machine? MA= DE DR MA= 10 m 10 m MA= 1
What is the MA of this machine? MA= DE DR MA= 40 m 20 m MA= 2 A man pulls a rope 40 meters to lift the box 20 meters off the ground
What is the MA of this machine? MA= 3 75 N 25 N 25 N 25 N 25 N 25 N EFFORT FORCE RESISTANCE FORCE MA= FR FE MA= 75 N 25 N
What is the MA of this machine? To calculate the Mechanical Advantage of a wheel and axle you must use this formula: MA= Radius of Wheel Radius of Axle 9 cm 3 cm MA= 9 cm 3 cm MA= 3
What is the MA of this machine? To calculate the Mechanical Advantage of an inclined plane you must use this formula: MA= Length of IP Height of IP 27 cm 3 cm MA= 27 cm 3 cm MA= 9
• A compound machine (complex machine) consist of two or more simple machines that work together to perform a function. • Generally, compound machines perform more complex functions than simple machines. • Example: • Bicycle COMPOUND MACHINES