Grade 7
  1. Introduction to Physics  1.1. Definition and scope of physics  1.2. Importance of Physics in Daily Life and Technology  1.3. Scientific method and its applications in physics  1.4. Measurement and Experiments in Physics  1.5. Branches of Physics and their Applications  1.6. Relation of physics with other sciences
  2. Measurement and units  2.1. Fundamental and derived quantities  2.2. SI units and unit conversions  2.3. Length measuring instruments and tools used  2.4. Measuring the difference between mass and weight  2.5. Measuring time with accuracy  2.6. Measuring the Volume of Regular and Irregular Objects  2.7. Measuring Temperature and Temperature Scales  2.8. Accuracy, Precision, and Significant Figures  2.9. Errors in Measurement and How to Reduce Them  2.10. Estimates and approximations in scientific calculations  2.11. Standard form and order of magnitude
  3. Speed and Force  3.1. Introduction to motion and rest  3.2. Types of motion - uniform and non-uniform  3.3. Scalars and vectors in motion  3.4. Speed, Velocity, and Acceleration  3.5. Distance-time and velocity-time graphs  3.6. Newton's first law of motion (law of inertia)  3.7. Newton's second law of motion (force and acceleration)  3.8. newton's third law of motion  3.9. Types of forces - contact and non-contact forces  3.10. Effect of forces on motion  3.11. Friction – types, effects and applications  3.12. Gravity, free fall and gravitational acceleration  3.13. Circular motion and centripetal force  3.14. Application of Newton's laws in real life
  4. Energy, Work and Power  4.1. Definition and forms of energy  4.2. Potential and Kinetic Energy  4.3. Law of conservation of energy  4.4. Energy transformations in everyday life  4.5. Work done by force and its calculation  4.6. Power - Definition and Calculation  4.7. Simple Machines and Mechanical Advantage  4.8. Efficiency and energy losses of machines  4.9. Renewable and non-renewable energy sources
  5. Heat and temperature  5.1. Difference Between Heat and Temperature  5.2. Thermometer and temperature scale (Celsius, Kelvin, Fahrenheit)  5.3. Expansion and contraction of solids, liquids and gases  5.4. Heat transfer methods – conduction, convection and radiation  5.5. good and bad conductors of heat  5.6. Applications of heat transfer in daily life  5.7. Specific heat capacity and its applications  5.8. Latent heat and change of state  5.9. Thermal equilibrium and heat exchange  5.10. effect of heat on matter
  6. Lighting and Optics  6.1. Nature and properties of light  6.2. Reflection of light and laws of reflection  6.3. Image formation by plane and curved mirrors  6.4. Refraction of light and the laws of refraction  6.5. Lenses – convex and concave, image formation  6.6. Optical instruments – microscope, telescope, camera  6.7. Dispersion of light and formation of spectrum  6.8. Human eye, vision defects and their correction  6.9. Applications of optics in daily life  6.10. Total internal reflection and its applications
  7. Sound and waves  7.1. Nature and properties of waves  7.2. Production and propagation of sound  7.3. Characteristics of sound waves – frequency, amplitude, wavelength  7.4. Speed of sound in different mediums  7.5. Reflection of sound – echo and reverberation  7.6. Ultrasound and its applications  7.7. Doppler effect in sound waves  7.8. Noise pollution and its effects  7.9. Applications of sound in medicine and industry
  8. Electricity and Magnetism  8.1. Electric charge and static electricity  8.2. Electrical conductors and insulators  8.3. Electric current, voltage and resistance  8.4. Ohm's law and its applications  8.5. Electrical Circuits - Series and Parallel Circuits  8.6. Electric power and energy consumption  8.7. Safety precautions in the use of electricity  8.8. Properties of magnets and magnetic fields  8.9. Electromagnets - How They Work and Their Uses  8.10. Relation between electricity and magnetism (electromagnetic induction)  8.11. Applications of electromagnetism in technology  8.12. Earth's magnetic field and its effects
  9. Matter and its properties  9.1. Classification of matter- solid, liquid and gas  9.2. Properties of different states of matter  9.3. Kinetic theory of matter  9.4. Changes in the state of matter and their causes  9.5. Expansion and contraction of substances  9.6. Density and its calculation  9.7. Pressure in solids, liquids and gases  9.8. Atmospheric pressure and its effects  9.9. Applications of pressure in daily life  9.10. Buoyancy and Archimedes' principle
  10. Space Science and Solar System  10.1. Introduction to Astronomy  10.2. Solar System - Planets and their Characteristics  10.3. Sun - structure and energy production  10.4. Moon - phases and its effect on Earth  10.5. Rotation and revolution of the earth  10.6. Solar and lunar eclipses  10.7. Gravity in space and its role in orbits  10.8. Artificial satellites and their uses  10.9. Space exploration and modern discoveries  10.10. Asteroids, comets and meteors  10.11. Life beyond Earth - Possibilities and Theories
  11. Environmental Physics  11.1. Impact of physics on environmental science  11.2. Renewable and non-renewable energy sources  11.3. Energy conservation and efficiency  11.4. Climate change and its effects on Earth  11.5. Air, water and soil pollution – causes and effects  11.6. Greenhouse effect and global warming  11.7. Sustainable development and environmental protection  11.8. Role of Physics in Weather and Climate Studies

Grade 7 → Energy, Work and Power ↓


Simple Machines and Mechanical Advantage


Have you ever wondered how the ancient Egyptians were able to build the pyramids or how cranes are able to lift heavy loads? The secret lies in the use of simple machines and the principle of mechanical advantage. This topic is not only fascinating but also very useful in our daily lives, as simple machines are all around us. In this comprehensive lesson, we will explore simple machines, how they work, and how they give us mechanical advantage in doing work.

What are simple machines?

Simple machines are basic mechanical devices for applying force. They provide a straightforward way to make tasks easier by increasing the force, changing its direction, or increasing the speed of movement. There are six classic types of simple machines which include:

  • lever
  • inclined plane
  • wheel and axle
  • pulley
  • screw
  • nail

Lever

A lever is a rigid bar that rests on a support called a fulcrum. By applying force at one end, the lever rotates around the fulcrum, effectively amplifying the input force to lift or move an object at the other end. Imagine a seesaw on a playground!

Effort Burden Base

The mechanical advantage (MA) of the lever is determined by the ratio of the distance from the fulcrum to the point where the effort is applied to the distance from the fulcrum to the point where the load is applied:

MA = Distance from Effort to Fulcrum / Distance from Load to Fulcrum

For example, if you have a 2 m lever bar whose fulcrum is located 0.5 m from the load, the distance from the effort to the fulcrum will be 1.5 m. Then:

MA = 1.5 / 0.5 = 3

This means that the effort applied at the end of the load will increase three times.

Inclined plane

An inclined plane is a flat surface tilted at an angle, allowing a load to be lifted up or down with less effort than lifting it straight up. Imagine pushing a heavy box up a ramp instead of lifting it straight up.

Length Height Increase

The mechanical advantage for an inclined plane is calculated as the ratio of the length of the plane to its height:

MA = Length of Incline / Height of Incline

This implies that the greater the inclination relative to the height, the greater is the mechanical advantage, making it easier to move a load upward.

Wheel and axle

A wheel and axle consists of a larger diameter wheel attached to a smaller diameter axle. When force is applied to the wheel, it turns the axle, or vice versa, creating motion.

radius

The mechanical advantage in a wheel and axle system is the ratio of the radius of the wheel to the radius of the axle:

MA = Radius of Wheel / Radius of Axle

This system allows a smaller force to be applied over a greater distance to efficiently drive a larger axle.

Pulley

A pulley consists of a wheel with a groove on its side, through which a rope or chain runs. Pulleys are useful for lifting loads vertically by redirecting the applied force.

Rope

Pulleys can be grouped together to form a block and tackle system, providing a mechanical advantage that can be calculated by counting the number of rope segments that support the load:

MA = Number of Rope Segments

More sections allow heavier loads to be lifted more easily.

Screw

A screw is essentially an inclined plane that is wrapped around a cylinder. This converts rotational force into linear motion, allowing the screw to penetrate material or lift a load.

The mechanical advantage of a screw depends on the ratio of its circular motion (circumference) and the distance between the threads:

MA = Circumference of Screw / Lead of Screw

This means that closely threaded screws provide more force over a shorter distance.

The wedge

A wedge is a simple machine that looks like a sharp inclined plane. It is used to separate two objects, or parts of an object, or to hold an object in place. Examples include knives, axes, and door closers.

Nail

Wedges convert the force applied to their blunt end into increased force at their sharp end, allowing substances to be separated or broken with less force.

Understanding mechanical advantage

Mechanical advantage (MA) is a measure of the force amplification achieved by using a tool, mechanical device, or machine system. It is calculated as the ratio of output force to input force. With simple machines, this concept helps us understand how to make work easier.

MA = Output Force / Input Force

In practical terms, mechanical advantage allows less force to be used to move a load. For example, pulling a lawnmower up a slope requires less force than lifting it straight up, which is due to the mechanical advantage of inclining.

Applications and text examples

Knowing about simple machines and mechanical advantage is not just academic. These concepts have everyday applications such as:

  • Use of a screwdriver: The spiral threads of a screw, combined with a screwdriver, convert rotational force into a much stronger linear force.
  • Opening bottles: A bottle opening device uses a lever and fulcrum system.
  • Moving heavy furniture: Dollies use wheels and axles.
  • Flag hoisting: The flag is hoisted by pulling down a rope in a pulley system.

Conclusion

Simple machines may be just that, but their importance cannot be overstated. Through the principle of mechanical advantage, they enable us to perform tasks that would otherwise require significant physical effort. By understanding and using simple machines, we harness the power of physics to make our lives easier, allowing us to work smarter, not harder.


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Simple Machines and Mechanical Advantage

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