UNIT 14 SIMPLE MACHINES Simple machine a device

UNIT 14 – SIMPLE MACHINES

• Simple machine – a device that is generally made of one moving part – helps in making work easier • Simple machines make work easier by: – Multiplying force – Multiplying speed – Changing the direction

LEVER • a bar that is free to turn about a fixed point • 3 parts of a lever: 1. fulcrum – pivot point or point at which the lever is resting 2. load – or resistance that needs to be carried or overcome 3. effort – or force needed to lift/carry or overcome the load

Parts of a lever

Effort needed to lift or move a load can be reduced by: • moving the fulcrum closer to the load • applying the effort further from the fulcrum

3 TYPES OF LEVERS: • First Class Lever = LOAD – FULCRUM – EFFORT • Second Class Lever = FULCRUM – LOAD – EFFORT - function of first class and second class levers is to multiply the effort applied in order to produce greater force • Third Class Lever = FULCRUM – EFFORT – LOAD - function of the third class levers is to multiply the speed of the effort applied so that work is done faster

3 Types of Levers • FIRST CLASS • SECOND CLASS • THIRD CLASS

FIRST CLASS LEVERS

SECOND CLASS LEVERS

THIRD CLASS LEVERS

PULLEY – helps us to lift an object 3 Types of Pulleys: 1. FIXED PULLEY – a pulley fixed to a support - effort moves downwards while load moves upwards - function = to change direction of the effort applied - does not reduce the effort needed to lift the load; effort and load move the same distance

FIXED PULLEYS

Types of Pulleys • MOVABLE PULLEY - a pulley that is not fixed to a support - the pulley moves together with the load - effort and load move in the same direction - function is to reduce the effort applied - effort moves a greater distance than the load

MOVABLE PULLEYS

Types of pulleys • PULLEY SYSTEM – made up of more than one pulley to lift a load - made up of fixed pulleys and movable pulleys - function is to multiply the effort applied to produce a greater force to lift the load - commonly used on ships; usually called a block and tackle

PULLEY SYSTEMS

WHEEL AND AXLE • • Made up of a wheel fixed to a rod called the axle. The wheel is bigger than the axle. When the wheel turns, the axle turns too. The wheel moves a greater distance than the axle. • Function is to multiply the effort applied to produce greater force. • The wheel multiplies the effort applied to move a load at the axle

WHEEL AND AXLE

INCLINED PLANE • A flat surface whose endpoints are at different heights • Easier to pull or push a load up an inclined plane • Function is to reduce the effort applied • The effort moves the objects over a greater distance

INCLINED PLANES

GEARS • Wheels with teeth on them • Function is to change the direction of the effort • Multiply the speed of the effort • When gears interlock, they turn together

GEARS

PRECAUTIONARY MEASURES IN USING SIMPLE MACHINES • Use the right type of simple machines for the right job to prevent injury caused by bending or breaking levers. • Secure pulleys properly before using them and ensure that pulleys can withstand the load being lifted. • Simple machines that are sharp should be handled with care. Always cover the sharp edges when storing or transporting them.

COMPLEX MACHINES • COMPLEX MACHINES – consists of several simple machines put together in order to work or operate • Parts of an airplane: - wheels - engines - wings - tail

COMPLEX MACHINES

• • http: //www. sciencebuddies. org/science-fair-projects/project_ideas/Phys_img 081. jpg http: //www. school-for-champions. com/science/images/machines_levers-pliers. gif http: //facstaff. gpc. edu/~pgore/Physical. Science/images/bottle-opener. jpg http: //www. diracdelta. co. uk/science/source/l/e/lever/wheelbarrow 001. jpg http: //juniorengineering. usu. edu/workshops/machines/images/lever 6. jpg http: //www. climatechangematters. net. au/LOTS/Phy/sub/levers/images/thumb_Lever 1. gif http: //www. gmasononline. com/LEVER 3. gif http: //www. legoeducation. us/sharedimages/content/Extra. Large/XL_DOORKNOB. jpg