SET 12

🎯 Objectives: TOWARD NECTA Physics - Set 12 Questions and Answers

SET 12: NECTA Form Four Physics Conceptual Questions and Answers (50 Questions)

  1. What is meant by displacement?
    Answer: Displacement is the shortest distance from the initial to the final position of a point, along with direction.
    Example: If you walk 5 m east then 3 m west, your displacement is 2 m east.
  2. Explain the difference between speed and velocity.
    Answer: Speed is the rate of change of distance and is scalar; velocity is speed in a specific direction and is a vector.
    Example: 50 km/h is speed; 50 km/h north is velocity.
  3. State the laws of reflection.
    Answer: (1) Angle of incidence equals angle of reflection.
    (2) Incident ray, reflected ray, and normal lie in the same plane.
    Example: Light reflecting off a mirror.
  4. Why do shadows change size during the day?
    Answer: Because the angle of the Sun changes, affecting the length of the shadow.
    Example: Morning shadows are long; noon shadows are shortest.
  5. What is meant by acceleration?
    Answer: Rate of change of velocity with time.
    Example: A car speeding up from 0 to 60 km/h.
  6. Why do objects fall towards the Earth?
    Answer: Due to gravitational force exerted by Earth pulling objects towards its center.
    Example: An apple falling from a tree.
  7. Define momentum.
    Answer: Momentum is the product of mass and velocity of an object.
    Example: A moving truck has more momentum than a moving bicycle.
  8. What causes friction?
    Answer: The irregularities on surfaces in contact and the electromagnetic forces between molecules.
    Example: Rubbing hands generate heat due to friction.
  9. What is the effect of friction on moving objects?
    Answer: It opposes motion and can cause wear and heat.
    Example: Brakes use friction to stop cars.
  10. Explain the difference between mass and weight.
    Answer: Mass is the amount of matter in an object; weight is the force of gravity acting on the mass.
    Example: Mass remains constant on Moon, weight changes.
  11. What is the unit of force?
    Answer: Newton (N).
    Example: Weight is measured in newtons.
  12. What is the principle of moments?
    Answer: For a body in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments.
    Example: Seesaw balanced by equal weights at different distances.
  13. Why does a car slow down when brakes are applied?
    Answer: Brakes apply friction which opposes the motion and converts kinetic energy into heat.
    Example: Car stopping at a traffic light.
  14. Define kinetic energy.
    Answer: Energy possessed by a body due to its motion.
    Example: Moving vehicles have kinetic energy.
  15. What factors affect the kinetic energy of a moving object?
    Answer: Mass and velocity of the object.
    Example: Doubling velocity quadruples kinetic energy.
  16. What is meant by work done?
    Answer: Work is done when a force causes displacement in the direction of the force.
    Example: Pushing a box across the floor.
  17. What is power?
    Answer: Power is the rate of doing work.
    Example: A motor that lifts a load faster has more power.
  18. What is meant by pressure?
    Answer: Pressure is force per unit area.
    Example: Sharp knife has more pressure than a blunt one.
  19. How does atmospheric pressure change with altitude?
    Answer: Atmospheric pressure decreases as altitude increases.
    Example: Mount Everest has low atmospheric pressure.
  20. What is density?
    Answer: Density is mass per unit volume.
    Example: Lead is denser than wood.
  21. What is the principle of flotation?
    Answer: An object floats if the weight is equal to the upthrust.
    Example: Boats float because they displace enough water.
  22. Why do hot air balloons rise?
    Answer: Hot air is less dense than cold air, creating buoyant force.
    Example: Balloon ascends when heated air is inside.
  23. Explain convection.
    Answer: Heat transfer by movement of fluid caused by differences in density.
    Example: Warm air rising above a heater.
  24. What is conduction?
    Answer: Heat transfer through a solid without movement of the solid.
    Example: Heating one end of a metal rod.
  25. Explain radiation.
    Answer: Transfer of heat by electromagnetic waves.
    Example: Heat from the Sun reaches Earth by radiation.
  26. Why are metals good conductors of heat?
    Answer: They have free electrons that transfer energy quickly.
    Example: Copper pans heat up fast.
  27. What is specific heat capacity?
    Answer: Amount of heat required to raise temperature of 1 kg of substance by 1°C.
    Example: Water has high specific heat capacity.
  28. What is latent heat?
    Answer: Heat absorbed or released during phase change without temperature change.
    Example: Ice melting into water.
  29. Define frequency of a wave.
    Answer: Number of waves passing a point per second.
    Example: High frequency means more waves per second.
  30. What is wavelength?
    Answer: Distance between two successive crests or troughs.
    Example: Radio waves have longer wavelength than light.
  31. Explain the Doppler effect.
    Answer: Change in frequency or pitch due to relative motion between source and observer.
    Example: Siren pitch changes as ambulance passes.
  32. What is an electromagnetic wave?
    Answer: Wave consisting of oscillating electric and magnetic fields that can travel through vacuum.
    Example: Light, radio waves.
  33. Why do objects appear colored?
    Answer: Because they reflect some wavelengths and absorb others.
    Example: Leaves appear green because they reflect green light.
  34. What is refraction?
    Answer: Bending of light when it passes from one medium to another.
    Example: Pencil looks bent in water.
  35. State Snell’s law.
    Answer: Ratio of sine of angle of incidence to sine of angle of refraction is constant.
    Example: Light bending entering water.
  36. What is total internal reflection?
    Answer: Reflection of all light inside a denser medium when angle of incidence exceeds critical angle.
    Example: Optical fibers.
  37. Why do stars twinkle?
    Answer: Atmospheric turbulence causes light to refract variably.
    Example: Twinkling seen from Earth.
  38. What is radioactive decay?
    Answer: Spontaneous breakdown of unstable nuclei emitting radiation.
    Example: Uranium decaying to lead.
  39. What is half-life?
    Answer: Time taken for half the radioactive atoms to decay.
    Example: Carbon-14 half-life.
  40. Define electric current.
    Answer: Flow of electric charge.
    Example: Current powering a bulb.
  41. What is voltage?
    Answer: Electric potential difference between two points.
    Example: Battery voltage.
  42. Explain Ohm’s law.
    Answer: Current is directly proportional to voltage at constant temperature.
    Example: V = IR.
  43. What is resistance?
    Answer: Opposition to current flow.
    Example: Thin wires have more resistance.
  44. Why does resistance increase with temperature in metals?
    Answer: Atoms vibrate more, hindering electron flow.
    Example: Heating filament increases resistance.
  45. What is a fuse?
    Answer: Safety device that melts to break circuit if current is too high.
    Example: Protects wiring from damage.
  46. What is the function of a transformer?
    Answer: Change AC voltage levels.
    Example: Step-up transformers in power lines.
  47. Why are superconductors important?
    Answer: They have zero resistance at very low temperatures.
    Example: Used in MRI machines.
  48. What is an electric motor?
    Answer: Device that converts electrical energy into mechanical energy.
    Example: Fans use electric motors.
  49. Explain the function of a capacitor.
    Answer: Stores electrical energy temporarily.
    Example: Camera flashes.
  50. What causes magnetic fields?
    Answer: Moving electric charges or magnetic materials.
    Example: Current-carrying wire produces magnetic field.
  51. What is electromagnetic induction?
    Answer: Generation of emf when magnetic flux changes in a coil.
    Example: Generators producing electricity.

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