Answers to 100 O’level Physics Questions.

Mechanics:

  1. What is the SI unit of force? Answer: Newton (N)
  2. Define displacement. Answer: Displacement is the change in position of an object in a particular direction.
  3. What is the equation for calculating speed? Answer: Speed = Distance / Time
  4. Define acceleration. Answer: Acceleration is the rate of change of velocity with respect to time.
  5. State Newton’s First Law of Motion. Answer: Newton’s First Law of Motion, also known as the law of inertia, states that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an external force.
  6. What is the formula for calculating weight? Answer: Weight = Mass × Acceleration due to gravity (usually taken as 9.8 m/s² on Earth’s surface)
  7. State Newton’s Second Law of Motion. Answer: Newton’s Second Law of Motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. It is given by the equation: F = ma, where F is the net force, m is the mass, and a is the acceleration.
  8. Define momentum. Answer: Momentum is the product of an object’s mass and velocity. It is a vector quantity.
  9. What is the principle of conservation of momentum? Answer: The principle of conservation of momentum states that the total momentum of an isolated system remains constant if no external forces act on it.
  10. Define friction. Answer: Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact.
  11. What is the equation for calculating pressure? Answer: Pressure = Force / Area
  12. State the principle of moments. Answer: The principle of moments states that for an object in equilibrium, the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about the same point.
  13. Define work in the context of physics. Answer: Work is done when a force is applied to an object, causing a displacement in the direction of the force.
  14. What is the equation for calculating work done? Answer: Work done = Force × Displacement × cos(θ) (where θ is the angle between the force and displacement vectors)
  15. Define power. Answer: Power is the rate at which work is done or energy is transferred or converted.
  16. State the principle of conservation of energy. Answer: The principle of conservation of energy states that energy cannot be created or destroyed; it can only be transformed from one form to another.
  17. What is the equation for calculating kinetic energy? Answer: Kinetic Energy = (1/2) × Mass × (Velocity)^2
  18. Define gravitational potential energy. Answer: Gravitational potential energy is the energy possessed by an object due to its position in a gravitational field.
  19. What is the equation for calculating gravitational potential energy? Answer: Gravitational Potential Energy = Mass × Acceleration due to gravity × Height
  20. Define elastic potential energy. Answer: Elastic potential energy is the energy stored in an elastic object when work is done on it to change its shape.
  21. What is the equation for calculating elastic potential energy? Answer: Elastic Potential Energy = (1/2) × Spring Constant × (Extension)^2
  22. Define Hooke’s Law. Answer: Hooke’s Law states that the extension of a spring is directly proportional to the force applied to it, provided the elastic limit is not exceeded.
  23. State the law of conservation of energy. Answer: The law of conservation of energy states that the total energy of an isolated system remains constant over time.
  24. Define density. Answer: Density is the mass per unit volume of a substance.
  25. What is the equation for calculating density? Answer: Density = Mass / Volume
  26. Define upthrust. Answer: Upthrust, also known as buoyant force, is the upward force exerted by a fluid on an immersed object.
  27. State Archimedes’ principle. Answer: Archimedes’ principle states that the upthrust (buoyant force) experienced by an object immersed in a fluid is equal to the weight of the fluid displaced by the object.
  28. What is the equation for calculating pressure in a fluid? Answer: Pressure in a fluid = Force / Area
  29. Define terminal velocity. Answer: Terminal velocity is the constant speed attained by a falling object when the upward force of air resistance equals the downward force of gravity.
  30. State the conditions required for an object to be in equilibrium. Answer: For an object to be in equilibrium, the vector sum of all forces acting on it should be zero, and the sum of all torques (or moments) acting on it about any point should be zero.

Waves:

31. Define wave motion. Answer: Wave motion is the transfer of energy through the propagation of disturbances in a medium without any net movement of the medium itself.

  1. What is the equation for calculating wave speed? Answer: Wave Speed = Frequency × Wavelength
  2. State the principle of superposition. Answer: The principle of superposition states that when two or more waves meet at a point in space, the resultant displacement at that point is the algebraic sum of the individual displacements.
  3. Define amplitude. Answer: Amplitude is the maximum displacement of a particle from its equilibrium position in a wave.
  4. What is the difference between transverse and longitudinal waves? Answer: In transverse waves, the direction of particle displacement is perpendicular to the direction of wave propagation, while in longitudinal waves, the direction of particle displacement is parallel to the direction of wave propagation.
  5. Define frequency. Answer: Frequency is the number of complete oscillations (or cycles) of a wave that pass a given point in one second.
  6. What is the relationship between frequency and wavelength? Answer: Frequency and wavelength are inversely proportional. As the frequency increases, the wavelength decreases, and vice versa.
  7. Define time period. Answer: Time period is the time taken for one complete oscillation (or cycle) of a wave.
  8. What is the relationship between time period and frequency? Answer: Time period and frequency are inversely proportional. Time period = 1 / Frequency, and Frequency = 1 / Time period.
  9. State the law of reflection. Answer: The law of reflection states that the angle of incidence is equal to the angle of reflection, and both angles are measured with respect to the normal to the reflecting surface.
  10. Define refraction. Answer: Refraction is the bending of a wave as it passes from one medium to another at an angle, due to a change in its speed.
  11. State Snell’s Law. Answer: Snell’s Law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. It is given by: n1 × sinθ1 = n2 × sinθ2, where n1 and n2 are the refractive indices of the two media.
  12. What is the critical angle in the context of refraction? Answer: The critical angle is the angle of incidence in a denser medium for which the angle of refraction in the rarer medium is 90 degrees. At the critical angle, light is refracted along the boundary and does not pass into the rarer medium.
  13. Define dispersion. Answer: Dispersion is the phenomenon of splitting light into its constituent colors (or wavelengths) as it passes through a prism or other dispersive medium.
  14. State the principle of superposition for waves. Answer: The principle of superposition for waves states that when two or more waves meet at a point in space, the resultant displacement at that point is the algebraic sum of the individual displacements.
  15. Define interference. Answer: Interference is the phenomenon that occurs when two or more waves superpose to form a resultant wave of greater or lesser amplitude.
  16. What is the difference between constructive and destructive interference? Answer: In constructive interference, the waves reinforce each other, resulting in a wave with a larger amplitude. In destructive interference, the waves cancel each other out, resulting in a wave with a smaller amplitude or no wave at all.
  17. Define diffraction. Answer: Diffraction is the bending of waves around obstacles or the spreading of waves as they pass through a narrow aperture.
  18. What is the relationship between diffraction and wavelength? Answer: The amount of diffraction is inversely proportional to the wavelength. Longer wavelengths diffract more than shorter wavelengths.
  19. Define resonance. Answer: Resonance is the phenomenon that occurs when the frequency of an applied force matches the natural frequency of an object, resulting in a significant increase in amplitude.

Electricity and Magnetism:

51. Define electric current. Answer: Electric current is the flow of electric charge in a conductor.

  1. What is the SI unit of electric current? Answer: Ampere (A)
  2. State Ohm’s Law. Answer: Ohm’s Law states that the current passing through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance of the conductor. It is given by the equation: I = V / R, where I is the current, V is the voltage, and R is the resistance.
  3. What is the relationship between current, voltage, and resistance in Ohm’s Law? Answer: Current (I) = Voltage (V) / Resistance (R)
  4. Define potential difference. Answer: Potential difference is the work done (or energy transferred) per unit charge in moving a positive test charge between two points in an electric field.
  5. What is the SI unit of potential difference? Answer: Volt (V)
  6. Define resistance. Answer: Resistance is the opposition offered by a material to the flow of electric current through it.
  7. What is the SI unit of resistance? Answer: Ohm (Ω)
  8. State the principle of conservation of charge. Answer: The principle of conservation of charge states that electric charge cannot be created or destroyed; it can only be transferred from one object to another.
  9. Define electromotive force (EMF). Answer: Electromotive force (EMF) is the energy supplied per unit charge by the battery or power source to maintain a potential difference across its terminals.
  10. What is the SI unit of EMF? Answer: Volt (V)
  11. Define electric power. Answer: Electric power is the rate at which electrical energy is transferred or converted in an electric circuit.
  12. What is the equation for calculating electric power? Answer: Electric Power = Current × Voltage
  13. Define series and parallel circuits. Answer: In a series circuit, components are connected end-to-end, and the current is the same through all components. In a parallel circuit, components are connected across each other, and the voltage is the same across all components.
  14. State Kirchhoff’s First Law (Kirchhoff’s Current Law). Answer: Kirchhoff’s First Law states that the total current entering a junction (or node) in a circuit is equal to the total current leaving that junction.
  15. State Kirchhoff’s Second Law (Kirchhoff’s Voltage Law). Answer: Kirchhoff’s Second Law states that the total sum of the electromotive forces (EMFs) in a closed loop of a circuit is equal to the total sum of the potential differences (voltages) across all the components in that loop.
  16. Define magnetic field. Answer: A magnetic field is a region in which a magnetic force can be detected.
  17. State the right-hand rule for magnetic fields. Answer: In the right-hand rule for magnetic fields, if you point your thumb in the direction of the current in a straight conductor, the direction of the magnetic field lines encircling the conductor can be determined by the curling of your fingers.
  18. What is the direction of the magnetic field around a current-carrying wire? Answer: The magnetic field lines around a current-carrying wire form concentric circles in a plane perpendicular to the wire’s length.
  19. Define electromagnetism. Answer: Electromagnetism is the branch of physics that deals with the study of electric and magnetic phenomena and their interrelation.
  20. State Faraday’s Law of electromagnetic induction. Answer: Faraday’s Law states that when the magnetic flux through a coil or circuit changes, an electromotive force (EMF) is induced in the coil or circuit.
  21. What is the relationship between the induced EMF and the rate of change of magnetic flux? Answer: The induced electromotive force (EMF) in a coil or circuit is directly proportional to the rate of change of magnetic flux through the coil or circuit.
  22. Define transformers. Answer: Transformers are devices that change the voltage of alternating current (AC) by mutual induction between two coils.
  23. State the formula for calculating the turns ratio of a transformer. Answer: Turns ratio (N) = Number of turns in the secondary coil / Number of turns in the primary coil
  24. Define direct current (DC) and alternating current (AC). Answer: Direct current (DC) is the flow of electric charge in a single direction, while alternating current (AC) is the flow of electric charge that periodically reverses direction.

Energy, Work, and Power:

76. Define kinetic energy. Answer: Kinetic energy is the energy possessed by an object due to its motion.

  1. What is the equation for calculating kinetic energy? Answer: Kinetic Energy = (1/2) × Mass × (Velocity)^2
  2. Define gravitational potential energy. Answer: Gravitational potential energy is the energy possessed by an object due to its position in a gravitational field.
  3. What is the equation for calculating gravitational potential energy? Answer: Gravitational Potential Energy = Mass × Acceleration due to gravity × Height
  4. Define elastic potential energy. Answer: Elastic potential energy is the energy stored in an elastic object when work is done on it to change its shape.
  5. What is the equation for calculating elastic potential energy? Answer: Elastic Potential Energy = (1/2) × Spring Constant × (Extension)^2
  6. Define specific heat capacity. Answer: Specific heat capacity is the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius (or Kelvin).
  7. What is the equation for calculating heat energy? Answer: Heat Energy = Mass × Specific Heat Capacity × Change in Temperature
  8. Define the first law of thermodynamics. Answer: The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, but it can be converted from one form to another.
  9. State the principle of conservation of energy. Answer: The principle of conservation of energy states that the total energy of an isolated system remains constant over time.
  10. Define the efficiency of a machine. Answer: Efficiency is the ratio of the useful output work done by a machine to the total input work applied to the machine, expressed as a percentage.
  11. What is the equation for calculating the efficiency of a machine? Answer: Efficiency = (Useful Output Work / Total Input Work) × 100%
  12. Define power. Answer: Power is the rate at which work is done or energy is transferred or converted.
  13. What is the equation for calculating power? Answer: Power = Work done / Time taken, or Power = Energy transferred / Time taken

Electromagnetic Spectrum and Optics:

90. Define the electromagnetic spectrum. Answer: The electromagnetic spectrum is the range of all frequencies of electromagnetic radiation, from radio waves to gamma rays.

  1. State the order of the electromagnetic spectrum from lowest to highest frequency. Answer: Radio waves, Microwaves, Infrared radiation, Visible light, Ultraviolet radiation, X-rays, Gamma rays
  2. Define the visible spectrum. Answer: The visible spectrum is the portion of the electromagnetic spectrum that can be detected by the human eye. It consists of different colors ranging from violet to red.
  3. State the colors of the visible spectrum in order from lowest to highest frequency. Answer: Violet, Indigo, Blue, Green, Yellow, Orange, Red
  4. Define reflection. Answer: Reflection is the bouncing back of light rays from a surface.
  5. State the law of reflection. Answer: The law of reflection states that the angle of incidence is equal to the angle of reflection, and both angles are measured with respect to the normal to the reflecting surface.
  6. Define refraction. Answer: Refraction is the bending of light as it passes from one medium to another at an angle, due to a change in its speed.
  7. State Snell’s Law. Answer: Snell’s Law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. It is given by: n1 × sinθ1 = n2 × sinθ2, where n1 and n2 are the refractive indices of the two media.
  8. Define dispersion. Answer: Dispersion is the phenomenon of splitting light into its constituent colors (or wavelengths) as it passes through a prism or other dispersive medium.
  9. What happens to the speed and wavelength of light as it enters a denser medium? Answer: When light enters a denser medium, its speed decreases, and its wavelength decreases. However, the frequency of light remains the same.

These are the answers to the 100 O level Physics questions. Please note that the complexity of the answers may vary depending on the specific level and syllabus of the O level Physics course.

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