Grade 9
  1. Mechanics  1.1. Motion  1.1.1. Types of motion  1.1.2. Distance and displacement  1.1.3. Speed and Velocity  1.1.4. Acceleration  1.1.5. Graphical representation of motion  1.1.6. Equations of motion  1.1.7. Uniform and non-uniform motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Relative speed  1.1.10. Circular motion  1.2. Laws of force and motion  1.2.1. The concept of force  1.2.2. newton's first law of motion  1.2.3. Newton's second law of motion  1.2.4. Newton's third law of motion  1.2.5. Inertia and types of inertia  1.2.6. Motion  1.2.7. Conservation of momentum  1.2.8. Application of Newton's laws in daily life  1.2.9. Types of Forces (Contact and Non-Contact)  1.2.10. Friction and its effects  1.3. Gravitational force  1.3.1. Newton's law of universal gravitation  1.3.2. Importance of Gravitational Force  1.3.3. Acceleration due to gravity  1.3.4. Free fall and weightlessness  1.3.5. Mass and weight  1.3.6. Variation of g with height and depth  1.3.7. Kepler's laws of planetary motion  1.3.8. Satellites and their orbits  1.4. Work, Energy and Power  1.4.1. Concept of work  1.4.2. Positive and negative actions  1.4.3. Work done by constant and variable force  1.4.4. Energy and its forms  1.4.5. Kinetic energy and potential energy  1.4.6. Law of conservation of energy  1.4.8. Commercial unit of energy  1.4.9. Work–energy theorem  1.5. Simple machines  1.5.1. Types of simple machines  1.5.2. Mechanical advantage  1.5.3. Machine efficiency  1.5.4. Levers and their types  1.5.5. Pulleys and Inclined Planes  1.5.6. Gears and their uses
  2. Properties of matter  2.1. States of matter  2.1.1. Solids, liquids and gases  2.1.2. Properties of different states of matter  2.1.3. Change in state of matter  2.1.4. Plasma and Bose–Einstein condensate  2.2. Density and pressure  2.2.1. Concept of density and relative density  2.2.2. Pressure in solids, liquids and gases  2.2.3. Pascal's law and its applications  2.2.4. Atmospheric pressure and its variations  2.2.5. Surface tension and capillarity  2.3. Buoyancy and Archimedes' principle  2.3.1. Buoyant force  2.3.2. Archimedes principle  2.3.3. Applications of Archimedes' Principle  2.3.4. floating and sinking objects  2.3.5. Theory of Flotation and Archimedes' Principle
  3. Heat and Thermodynamics  3.1. Temperature and heat  3.1.1. Concept of heat and temperature  3.1.2. Temperature measurement  3.1.3. Temperature scales  3.2. Heat transfer  3.2.1. Conduction of heat  3.2.2. Convection of heat  3.2.3. heat radiation  3.2.4. Applications of heat transfer  3.2.5. Thermal conductivity  3.3. Thermal expansion  3.3.1. Expansion of solids, liquids and gases  3.3.2. Abnormal expansion of water  3.3.3. Applications of Thermal Expansion  3.4. Specific heat capacity and latent heat  3.4.1. Concept of specific heat capacity  3.4.2. Measurement and applications of specific heat  3.4.3. Latent heat of fusion and vaporization  3.4.4. Heat Engines and Efficiency
  4. Waves and sound  4.1. Waves and their types  4.1.1. Mechanical and electromagnetic waves  4.1.2. Longitudinal and Transverse Waves  4.1.3. Properties of Waves  4.1.4. Wavelength, frequency and speed of the wave  4.1.5. Superimposition of waves  4.2. Sound waves  4.2.1. Nature and transmission of sound  4.2.2. Speed of sound in different mediums  4.2.3. Reflection of sound and echo  4.2.4. Sonar and ultrasound  4.2.5. Resonance and pulsation  4.3. Sound characteristics  4.3.1. Intensity, loudness and quality of sound  4.3.2. Doppler effect in sound
  5. Lighting and Optics  5.1. Reflection of light  5.1.1. Laws of reflection  5.1.2. Reflection from a plane mirror  5.1.3. Reflection from a spherical mirror  5.1.4. Image formation by concave and convex mirrors  5.1.5. Applications of Reflection  5.2. Refraction of light  5.2.1. Laws of refraction  5.2.2. Refractive index  5.2.3. Refraction through a glass slab  5.2.4. Refraction in water and air  5.2.5. Lenses and their types  5.2.6. Image formation by convex and concave lenses  5.2.7. Total internal reflection and its applications  5.3. Dispersion and scattering of light  5.3.1. Spectrum of white light  5.3.2. Prisms and Dispersion  5.3.3. Tyndall effect and blue sky
  6. Electricity and Magnetism  6.1. Electric charge and static electricity  6.1.1. The concept of electric charge  6.1.2. Charging by friction, contact and induction  6.1.3. Electroscope and its working  6.2. Current Electricity  6.2.1. The concept of electric current  6.2.2. Ohm's Law and Resistance  6.2.3. Factors affecting resistance  6.2.4. Series and Parallel Circuits  6.2.5. Heating effect of electric current  6.2.6. Electric power and energy  6.3. Magnetism  6.3.1. Natural and artificial magnets  6.3.2. Properties of magnets  6.3.3. Earth's magnetism  6.3.4. Magnetic field and field lines  6.3.5. Electromagnets and their applications
  7. Modern Physics  7.1. structure of the atom  7.1.1. Atomic Structure and Subatomic Particles  7.1.2. Electrons, Protons, and Neutrons  7.1.3. Rutherford and Bohr model  7.2. Radioactivity  7.2.1. Types of radioactive emissions  7.2.2. Half-life and radioactive decay  7.2.3. Uses and Hazards of Radioactivity
  8. Space science and astronomy  8.1. The universe and its components  8.1.1. Stars and galaxies  8.1.2. Planets and Solar System  8.2. Satellites  8.2.1. Natural and artificial satellites  8.2.2. Use of satellites

Grade 9 → Mechanics → Simple machines ↓


Types of simple machines


Have you ever tried to lift something very heavy? It can be quite difficult. But imagine if you had a special device that made lifting easier. That's what simple machines do. They help us do work more easily. Simple machines are basic mechanical devices that make it easier to apply force and do work. Let's learn about the different types of simple machines.

Lever

A lever is a rigid bar that rotates around a fixed point called a fulcrum. It helps to lift or move a load with less effort. The seesaw on the playground is a great example of a lever. You might have noticed that when a person sits on it, one end of it goes down while the other end is raised.

Base

There are three classes of levers:

  1. First-class levers: This is the fulcrum between the effort and the load. Examples include seesaws and scissors.
  2. Second-class levers: The load is between the fulcrum and the effort. Examples include the wheelbarrow and the nutcracker.
  3. Third-class levers: The force is applied between the fulcrum and the load. Examples include forceps and fishing rods.

Pulley

A pulley has a wheel with a rope or cable wrapped around it. The pulley can change the direction of the force, making it easier to lift a load. Imagine a flagpole; when you pull the rope down, the flag goes up.

Pulley

By connecting pulleys, a system can be created that requires less force to lift a heavy object. This is known as a block and tackle system.

Inclined planes

An inclined plane is a flat surface set at an angle to the horizontal. This helps lift heavy objects by pushing or pulling them up a slope rather than lifting them straight up. A common example of this is a ramp.

Inclined plane

By increasing the length of the slope, less force is required to move an object up the slope. The disadvantage is that the object has to be moved a greater distance.

Wedges

A wedge is a tool that is thick at one end and thin at the other, used to break, cut, or lift objects. Doors and axes are good examples of wedges.

Nail

The nail converts the force applied at its thick end into a force applied at its thin end. It is especially useful in cutting and ripping operations.

Screws

A screw is an inclined plane that is wrapped around a cylinder. It converts rotational force into linear force. Screws are used to hold things together or lift materials. Think of how a screw is used to join pieces of wood or how a bottle cap works.

Screw

By turning the screw you apply a small force over a long distance, which makes the screw apply a large force over a short distance.

Wheel and axle

A wheel and axle is a large wheel attached to a smaller axle, the two rotating together. By applying force to the wheel, a load is moved or carried. A doorknob is an example of a wheel and axle.

Wheel and axle

This system amplifies the force applied, making movement of objects attached to the spindle easier.

Combination of simple machines

In many tools and machinery, simple machines are combined to perform complex tasks. For example, bicycles use wheels and axles, levers (as pedals), and pulleys (inside gear mechanisms) to make riding efficient.

Another example is a car jack, which combines screws and levers to easily lift a vehicle for repairs.

Calculating mechanical advantage

One of the main advantages of using simple machines is that they provide mechanical advantage. Mechanical advantage is the ratio of output force to input force. It shows how much easier a machine makes a task.

Lever

The mechanical advantage of a lever can be calculated using the following formula:

MA = Length of Effort Arm / Length of Load Arm

Where MA is the mechanical advantage, effort arm is the distance from the fulcrum to the point where the effort is applied, and load arm is the distance from the fulcrum to the load.

For example, if the effort arm is 4 m and the load arm is 1 m, then the mechanical advantage is:

MA = 4 / 1 = 4

This means that the lever makes the work 4 times easier.

Pulley

For pulleys, the mechanical advantage depends on the number of rope segments supporting the load. Each supporting rope supports a fraction of the total load, reducing the force required.

Inclined plane

The mechanical advantage of an inclined plane is given by:

MA = Length of Incline / Height of Incline

If the length of the ramp is 10 m and the height is 2 m, then:

MA = 10 / 2 = 5

This means that 5 times less force will be required than the force used to lift the object vertically.

Screw

The mechanical advantage for screws is a little more complicated. It involves the circumference of the screw and the pitch (the distance between the threads). The formula is:

MA ≈ 2πr / Pitch

where r is the radius of the screw.

Wheel and axle

The mechanical advantage of a wheel and axle can be calculated as follows:

MA = Radius of Wheel / Radius of Axle

For example, if the radius of the wheel is 40 cm and the radius of the axle is 10 cm, then the mechanical advantage is:

MA = 40 / 10 = 4

This means that the machine multiplies the force by 4, making the work easier.

In conclusion, simple machines are an integral part of everyday life, helping to complete tasks with efficiency and ease. Understanding how simple machines work allows us to appreciate the science behind the common tools and equipment we use. Through levers, pulleys, inclined planes, wedges, screws, and wheel and axle systems, we are able to perform tasks more effectively using the principles of mechanics and physics.


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Types of simple machines

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