2. SIMPLE & COMPOUND MACHINES
Students’ Learning Outcomes
· What is the simple machine?
· Demonstrate how wedge and incline plane are used to move the objects.
· Compare the three kinds of levers using example.
· Describe how lever makes work easier by giving examples of its uses from daily life.
INTRODUCTION
A machine is a device that does a physical task. Some machines make moving or lifting things easier. Other machines carry people from place to place. Yet other machines help in building or making things.
Simple machines makes work easier for us by allowing us to push or pull over increased distanced.
There are 6 basic simple machines; the lever, the wheel and axle, the inclined plane, the wedge, the pulley, and the screw. Several of these simple machines are related to each other. But, each has a specific purpose in the world of doing work. But what is work? Work is the amount of energy necessary to move an object.
how do simple machines work?
The basic principle of simple machines is that a force is applied at one point and transmitted to another point. The applied force is the input force manifested at the output as the output force.
Simple machines can accomplish one or more of the following functions:
Transfer force from one point to another
Change the direction of the force
Increase the magnitude of the force
Increase the distance or speed of the force
videos
The most basic machines are called simple machines. They are the inclined plane, the wedge, the lever, the wheel and axle, the screw, and the pulley. Simple machines change the strength or direction of a force, such as a push or pull.
A lever consists of a beam resting on a support. When a force is applied at a point on the beam, it rotates about the support point. The function of a lever is to multiply the applied force so that a heavy object can be raised. The applied force is called effort, the object is the load, and the support is the fulcrum or pivot.
An inclined plane is the simplest of all simple machines. It does not consist of any moving parts, neither does it move. An inclined plane consists of a slope that makes a fixed angle to the surface on which it rests. It moves an object from a lower level to a higher level without taking it vertically. In other words, the force applied to the object is less than its weight.
A wedge has a triangular shape and comprises one or two incline planes. A wedge works by changing the direction of the applied force, enabling it to cut through materials. The difference between an inclined plane and a wedge is that a wedge moves, whereas an inclined plane remains still. Examples: knife, axe, scalpel, and shovel.
A wheel and axle consists of a large disc (wheel) and a long rod or shaft (axle). A rotational force or torque is applied to one part, which then rotates and transmits the force to the other part. Mechanical advantage is gained by increasing the size of the wheel. A wheel and axle has many functions, including transporting and lifting objects. Bicycles and cars are equipped with wheels and axles to roll over large distances. Besides, rolling over a surface generates less friction than sliding.
A pulley consists of a wheel that rotates about its axis. A rope passing over the wheel is pulled to lift objects. Combining two or more pulleys allows one to raise heavy objects off the ground using minimum effort. In this way, the mechanical advantage is increased. Based on its design, a pulley can be of three types – fixed pulley, moveable pulley, and compound pulley.
A screw is a circular device in which a narrow inclined planed is wrapped around a cylinder, like a spiral staircase. One end of the screw forms the head, and the other end is sometimes pointed and forms the tip. A screw works on the principle of converting circular motion into translational motion.
2.2 compound machines
A compound machine consists of two or more simple machines. Examples of compound machines include bicycles, cars, scissors, and fishing rods with reels. Compound machines generally have lower efficiency but greater mechanical advantage than simple machines.
A bicycle is an example of a compound machine that uses a chain to transfer force. The chain runs around two separate toothed wheels, which act as pulleys.
videos about compound machines
examples of compound machines
1. Scissors
A pair of scissors is a prominent example of complex machines. It is made up of two simple machines, namely a wedge and a lever. The blades of the scissors are wedge-shaped, whereas the handles of the scissors act as the first-class lever.
2. Wheelbarrow
A wheelbarrow is a combination of three simple machines, namely, an inclined plane, a wheel and axle combination, and a lever. The container of the wheelbarrow is an inclined plane that helps store the load easily. The handles of the wheelbarrow act as levers, allowing the user to lift the load easily. The wheel attached to the base of the wheelbarrow is the wheel and axle arrangement that helps the machine move from one place to another with ease.
3. Can Opener
A can opener comprises four simple machines, namely, lever, gear, wheel and axle, and wedge. The arms of the can opener act as two levers that help to grip and open the can. The cutter attached to the mouth of the opener is a wedge that helps the machine pierce right through the metallic body of the can. The round part attached to the opener is the gear that rotates and helps the user hold the can still. The rotating handle is the wheel and axle simple machine that supplies energy to the gear and the wedge.
4. Stapler
A stapler is a complex machine that is made up of two simple machines, namely, a lever and a wedge. The punching mechanism of the stapler acts as the second-class lever, whereas the stapler pins act as the wedges. When the user applies push force to the lever of the stapler, the wedge-shaped stapler pin pierces through the papers, thereby simplifying the task of attaching two papers together.
5. Shovel
A shovel is a compound machine that is a combination of a wedge and a lever simple machine. The arm of the shovel acts as a third-class lever, while the tip of the shovel is a wedge. The lever helps the user move the shovel, and the wedge helps it penetrate the heap of soil or the ground with ease.
6. Fan
An electric fan is an example of a compound machine. It consists of a wedge simple machine and a combination of wheel and axle. The blades of an electric fan are wedge-shaped, which helps to maintain an even flow of air in the room. The rotation of the blades takes place around the hub. Hence, the rotating blades represent the wheel, while the hub acts as an axle.
PROJECTS:
SIMPLE MACHINES LAPBOOK PROJECT
SimpleMachinesLapbookandFoldables.pdf