Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Mechanics → Gravitational force ↓


Weight and apparent weight


Gravity is a fundamental concept in physics that explains the attraction between objects with mass. It is a topic that deeply affects our daily lives, from the way we walk to the way objects fall to the ground. Here, we will explore the concepts of weight and apparent weight, which are important concepts in understanding gravity. These concepts have both practical and theoretical applications in various areas of physics.

Understanding weight

Weight is a measure of the force of gravity acting on an object. It depends on the mass of the object and the gravitational acceleration acting on it. In everyday language, weight is often confused with mass. However, in physics, they are different concepts.

Mathematically, weight (W) is the product of mass (m) and gravitational acceleration (g). It can be represented by the formula:

W = m × g

Where:

  • W is the weight of the object, measured in newtons (N).
  • m is the mass of the object, measured in kilograms (kg).
  • g is the gravitational acceleration, which is about 9.8 m/s² on Earth.

Example:

If your mass is 50 kg, your weight on Earth will be:

W = 50 kg × 9.8 m/s² = 490 N

This means that the Earth exerts a force of 490 N on you, pulling you toward its center.

Finding the direct weight

Apparent weight is the normal force applied to an object or the force exerted by a surface to support the weight of an object. It may differ from the actual weight due to various conditions such as acceleration.

For example, when you are in a lift moving upwards, you feel heaviness. This feeling is due to the increase in your weight because of the upward movement.

Formula for direct weight

The apparent weight can be calculated using the following formula:

W a = m × (g ± a)

Where:

  • W a is the apparent weight.
  • a is the acceleration of the system (positive upwards, negative downwards).

Example of upward acceleration:

Imagine that you have a mass of 50 kg and you are in an elevator moving upward at 2 m/s². Your apparent weight would be:

W a = 50 kg × (9.8 m/s² + 2 m/s²) = 590 N

Due to upward acceleration your apparent weight increases.

Example of downward acceleration:

If the same lift accelerates downwards at a speed of 2 m/s², then the apparent weight becomes:

W a = 50 kg × (9.8 m/s² - 2 m/s²) = 390 N

Your apparent weight decreases, making you feel lighter. If the elevator were in free fall, your apparent weight would be zero, creating a feeling of weightlessness.

Visual explanations

Let's create a visual example using SVG to demonstrate the concept of weight and apparent load in an elevator scenario.

Lift Mass Weight (W = mg)

The figure above shows a simplified illustration of an elevator with a mass inside it. The forces acting on the mass, such as its weight and the direction of acceleration, affect its apparent weight.

Weightlessness

The concept of weightlessness occurs when the apparent weight of an object becomes zero. This can occur in free fall, or when an object is in orbit, as there is no contact force exerted by the surface. Astronauts in space experience this weightlessness because they are in a constant state of free fall orbit around the Earth.

To understand how this works, think of a satellite orbiting the Earth. Even though gravity acts on the satellite, it falls freely with it, resulting in no normal force acting on it. The sensation experienced by astronauts in this scenario is as if they were floating.

Real-life applications and examples

The concepts of load and apparent load are not only theoretical but also play an important role in many real-world applications.

Weighing machines

Weighing machines or scales measure your direct weight. When you stand on the scale, the scale measures the normal force, which is affected by acceleration conditions. This is why if you jump onto the scale, it shows a higher value momentarily because you apply extra force on it during the jump.

It's important to note that these machines usually don't measure the force of gravity directly, but rather the force exerted by the surface of the scales against your weight.

Amusement park rides

The change in weight is clearly evident in a roller coaster ride. As the ride moves downward, you may feel lighter, or even experience weightlessness for a brief period at the top of the loop. Conversely, when the ride moves upward, you may feel heavier due to the increased weight.

The physics behind rockets and space travel

The principles of weight and apparent weight are important in understanding the dynamics of rockets and space travel. When a rocket is launched, its apparent weight is incredibly high due to the rapid upward acceleration required to escape Earth's gravitational pull.

Once in orbit, the rocket and its contents experience weightlessness as they are in free fall around Earth. This allows astronauts to float in the cabin, an experience that is both exciting and challenging for performing everyday tasks.

Conclusion

The concepts of weight and apparent weight are fundamental in understanding how gravity affects us and the objects around us. By working through mathematical examples and visual depictions, we can better understand the underlying mechanics of measuring and experiencing weight in various scenarios. With this knowledge, we can delve further into advanced topics in physics and gain a solid understanding of how gravitational forces interact with mass.


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Weight and apparent weight

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