๐ง Topic: Machine (Form Three)
1. Meaning of a Machine
A machine is a device that makes work easier.
It helps us to apply a small force to move a large load or to change the direction of a force.
2. Types of Machines
There are two main types of machines:
- Simple machines
- Complex (compound) machines
(a) Simple Machines
These are machines with few or no moving parts.
Examples:
- Lever
- Pulley
- Inclined plane
- Wheel and axle
- Screw
- Wedge
(b) Compound Machines
These are made up of two or more simple machines working together.
Examples:
- Bicycle
- Sewing machine
- Car jack
3. Terms Used in Machines
| Term | Meaning |
|---|---|
| Effort (E) | The force applied to make the machine work |
| Load (L) | The weight or resistance moved by the machine |
| Mechanical Advantage (M.A) | The ratio of Load to Effort (M.A = L / E) |
| Velocity Ratio (V.R) | The ratio of the distance moved by effort to distance moved by load (V.R = DE / DL) |
| Efficiency (ฮท) | The ratio of useful work output to work input, usually in percentage |
Formula:
\text{Efficiency} = \frac{M.A}{V.R} \times 100\%4. Examples of Simple Machines
(a) Lever
A rigid bar that rotates around a fixed point called a fulcrum.
Types of levers:
- First Class Lever – Fulcrum is between effort and load (e.g. seesaw, crowbar).
- Second Class Lever – Load is between fulcrum and effort (e.g. wheelbarrow).
- Third Class Lever – Effort is between fulcrum and load (e.g. fishing rod, human arm).
(b) Pulley
A wheel with a groove over which a rope or chain passes.
- Fixed Pulley: Changes the direction of the force.
- Movable Pulley: Reduces the effort needed to lift a load.
- Block and Tackle: Combination of pulleys that increases mechanical advantage.
A flat surface set at an angle to the horizontal.
Example: ramp, staircase.
It reduces the effort needed to raise a load.
(d) Wheel and Axle
A large wheel fixed to a smaller axle; turning the wheel makes the axle turn.
Example: steering wheel, door handle.
(e) Screw
An inclined plane wound around a cylinder.
Example: screw jack, bolt.
(f) Wedge
Two inclined planes joined back to back.
Example: knife, axe, chisel.
5. Importance of Machines
- Make work easier
- Multiply force or speed
- Change direction of force
- Save time and energy
- Used in industries, homes, and transport
A machine lifts a load of 200 N by applying an effort of 50 N.
If the velocity ratio is 6, find:
- The mechanical advantage
- The efficiency
Solution:
7. Summary
- Machines make work easier.
- Key formulas:
- M.A=L/E
- V.R=DE/DL
- E.M=M.A/V.R×100%
- Simple machines include lever, pulley, inclined plane, screw, wedge, and wheel & axle.
๐ Understanding Energy and Power: The Backbone of Modern Life
๐น Introduction
Energy and power are two of the most important concepts in science and daily life. Every machine, light bulb, moving car, and living organism depends on energy to function. Without energy, life as we know it would not exist. Power, on the other hand, tells us how fast energy is used or produced. Understanding these two concepts helps us appreciate technology, protect our environment, and use resources wisely.
In this post, we will explore what energy and power mean, their types, sources, units, and their importance in the modern world.
⚡ What is Energy?
Energy is the ability to do work or cause change. It allows things to move, heat up, or produce light and sound. For example:
1.When you push a swing, you give it kinetic energy (energy of motion).
2.When you light a candle, chemical energy in the wax is changed into heat and light energy.
3.The sun provides solar energy that plants use to make food through photosynthesis.
4.Energy exists in many forms and can change from one form to another, but it cannot be created or destroyed. This principle is known as the Law of Conservation of Energy.
๐ Forms of Energy
There are many forms of energy, and all can be classified into two main categories: Potential Energy and Kinetic Energy.
1. Potential Energy
This is stored energy that has the potential to do work. Examples include:
1.Gravitational energy – a rock at the top of a hill.
2.Elastic energy – a stretched rubber band.
3.Chemical energy – energy stored in fuels, food, or batteries.
2. Kinetic Energy
This is the energy of motion. Any object that is moving has kinetic energy. Examples include:
1.Flowing water turning a turbine.
2.A moving car.
3.Wind blowing across the land.
Other specific forms of energy include:
1.Thermal energy – energy due to heat.
2.Electrical energy – energy caused by the movement of electrons.
3.Nuclear energy – energy released from atoms.
4.Radiant energy – energy from light or electromagnetic waves.
๐ What is Power?
While energy tells us how much work can be done, power tells us how fast that work is done.
Mathematically:
\text{Power} = \frac{\text{Energy}}{\text{Time}}
In simple terms, power measures the rate of energy transfer or rate of doing work.
For example:
1.A 100-watt light bulb uses energy faster than a 60-watt bulb.
2.A strong motor (high power) can lift heavy loads in a short time.
๐งฎ Units of Energy and Power
Quantity Definition SI Unit Symbol
Energy Ability to do work Joule J
Power Rate of doing work Watt W
1 Watt (W) = 1 Joule per second (J/s)
For larger scales:
1 kilowatt (kW) = 1,000 watts
1 megawatt (MW) = 1,000,000 watts
๐ Sources of Energy
Energy can come from renewable or non-renewable sources.
๐ 1. Renewable Energy Sources
These sources can be naturally replaced and are environmentally friendly.
Solar energy – from the sun.
Wind energy – from moving air.
Hydropower – from flowing water.
Geothermal energy – from heat inside the Earth.
Biomass energy – from organic materials like plants and animal waste.
⛽ 2. Non-Renewable Energy Sources
These sources are limited and can be exhausted over time.
Coal
Oil
Natural gas
Nuclear fuels (uranium)
๐ฑ The Importance of Energy in Daily Life
*Energy is vital in every sector of modern society:
*In homes: for cooking, lighting, heating, and powering devices.
*In industries: for running machines, manufacturing products, and transportation.
*In schools: for powering computers, projectors, and online learning.
*In healthcare: for running hospitals, preserving medicines, and performing operations.
Without energy, progress and comfort would be impossible.
๐ The Global Energy Challenge
As the world population grows, the demand for energy increases rapidly. Unfortunately, most of the world still depends on fossil fuels, which cause pollution and climate change.
This has led to:
*Global warming
*Air and water pollution
*Habitat destruction
To solve this, countries are investing in clean energy technologies, like solar panels, wind turbines, and electric vehicles.
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