Back to: Jss2 Basic Science (BST)
Topic: Simple Machines
WEEK: 6 & 7
A machine is an arrangement that makes it easy to do work on a load or against resistance.
A simple machine is the most basic kind of machine. They are things that work by using energy. When a small amount of force is used to overcome a large amount of resistance, the machine does the work.
A machine is a tool or set of tools that let a force (or effort) applied at one point overcome a load (or resisting force) at another point.
Simple machines like the lever, the pulley, the inclined plane, the wedge, the wheel and axle, the screw, and the hydraulic press can be put into different groups.
Some common examples of simple machines are scissors, drill braces, shovels (a type of lever), the pulley at the top of a flagpole, the steering wheel of an automobile (a type of wheel and axle), and wheelchair ramps (a form of inclined plane). The can opener is a simple example of a machine with many parts. It has a lever (the handle with the hinge), a wheel and axle (the turning knob), and a wedge (the sharpened cutting disk).
Types of Machine
This is an example of a simple machine. Knives, forks, spoons, and other kitchen tools are all examples of simple machines that we use every day.
A lever is made up of three parts: the effort, the load, and the fulcrum. The point where force is applied is called the Effort, the point where work is done is called the Load, and the point where something turns is called the Fulcrum.
Classes Of Lever
- First-class lever: is where the fulcrum is between the load and the effort e.g seesaw, crowbar, pliers etc.
- Second class lever: is where the load is between the fulcrum and the effort e.g wheelbarrow, nutcracker, bottle top opener, etc.
- Third class lever: is where the effort is between the fulcrum and the load e.g tweezers, sugar tong, table knife, cutlass.
Wheel And Axle
This simple machine is used to get heavy things out of deep places. It has a big wheel on a small axle that spins around the same axis. Bicycles, fans, waggons, and others are all made with wheels and axles.
Use Of Wheel And Axle
It is used to pull heavy loads out of deep water.
It is used to make the effect of a bicycle turning.
A simple machine is a screw thread. A simple screw is just a rod with a thread on it. The space between two threads is called the Pitch, and the screw’s handle is called the Effort. It is where the effort is put into the rotation.
For screws to work, when the effort moves the load a full circle’s circumference, the effort must move the load the same amount.
Screws come in different shapes, depending on what they are used for and what tools are used to put them in place. Most wood screws, which are used to hold wood together, have pointed tips.
Uses Of Screw Thread
Screw thread can be used to:
Screw thread can be used to:
Used to make holes in hard things like wood and soft iron.
3. To put mirrors in place.
4. To attach accessories to metal window frames.
A pulley is a simple machine that makes lifting a load easier by reducing the amount of force needed. A block, a wheel, and a rope or chain are the parts that make up a pulley. The more pulleys or ropes are used, the more weight can be moved and less force is needed.
In the form of cranes, builders use pulleys to move heavy loads to higher floors. It is also used to move heavy goods into and out of ships at docks.
Since the Middle Ages, people have used pulley systems to move heavy things. The block and tackle and the chain hoist are two well-known types of pulley systems. Most chain hoists are run by hand, while block and tackle systems are often run by an engine or motor.
The Wedge And Inclined Plane
An inclined plane is a simple machine that looks like a sloped plane. It is used to lift heavy things that can’t be lifted by hand. It is easier to push a heavy load up a slope to a certain height than to lift it to that height. A tilted plane makes it easier to lift heavy things because a person can use the force they need over a long distance.
One of the four simple machines is the inclined plane (along with the lever, the wheel and axle, and the pulley). The screw and the wedge are two other simple machines that are really just different kinds of the inclined plane.
One of the most common examples of an inclined plane is a staircase, which lets people move from one floor to another in a building with less effort than it would take to climb straight up a ladder. Threaded screws are used in some car-lifting jacks.
A knife is a wedge that people use every day. Other examples are scissors, saws, axes, nails, and anything else with a blade.
Some parts of a machine, like gears, belt and chain drivers, brakes, clutches, and bearings, are used to move one part to the next.
How Gears Wor:
Gears are like a long lever, just like the wheel and axle. Depending on the diameter or number of teeth on the driven gear to the driving gear, they can be used as either a force multiplier or a distance multiplier.
Bevel gears can also be used to change the direction of motion at a right angle. In a gearing system, the larger wheel always moves slower but with more force, while the smaller wheel moves faster but with less force.
Belt and Chain Drives
Energy is the power to get things done. There are different kinds of energy, like heat, light, mechanical energy, potential energy, and electrical energy. Measures of energy: The joule (J) or the newton-meter (N * m) is the SI unit of energy. The SI unit of work is also the joule. from one shaft to another when the distance between both shafts is more than what the gears need. Most belt drives are either open drives or cross drives. Most belt drives work because of friction.
Belt drive is made up of pulleys that a belt, usually made of rubber but sometimes made of other materials, goes around.
The pulleys are attached to shafts that turn. The pulleys can be flat or have grooves on them. In a belt drive, the speed at which the shafts turn can’t be kept constant. Belt drives are often found in sewing machines, pepper grinders, and melon grinders.
When it’s important to keep the shaft turning at the same speed and make the drive safer, the chain drive is used. Bikes, motorcycles, and cars are all common places to find chain drives.
A chain drives a bicycle.
Brakes and Clutches
The main job of a brake is either to stop a moving object or to keep an object at rest or in a steady motion despite the action of outside forces. Friction is used to make brakes work. You can have a simple block brake, a band brake, or a shoe brake. Shoes can be on the inside or the outside. The shoe brake is made up of two shoes that move on pivots and have special friction material on the inside.
A hydraulic system applies force to the brake, which forces the shoes to touch the inside cylinder surface of the brake drum, which is fixed to the road wheels. The car stops moving when there is enough friction between the brake down and the surface of the shoe.
Clutches are used to transfer motion from a driving shaft to a driven shaft or to stop such motion, depending on what is needed. Friction clutches are very common, and they work by using friction to transfer motion from a driving shaft to another shaft.
The friction clutch can be made of a single plate or a disc. Most cars have clutches that have only one plate. Most of the time, the plate clutches are mounted on a driven shaft close to the flywheel on the driving shaft, where the friction surfaces of the plates can make good contact to transfer motion.
Maintenance Of Machine
Maintenance is the care that is done on machines on a regular basis to keep them in good working order. Machines need to be taken care of regularly to:
i. Make sure they work well.
ii. Make sure machines move smoothly.
iii. Stop or stop a complete breakdown from happening.
iv. Replace machine parts that have broken down.
Here are some ways to take care of machines:
- Clean regularly to get rid of dirt.
- Oiling or making smooth.
- Regular checking.
- Service done regularly.