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[O] Pure Physics Smart Guides

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  1. SECTION I: MEASUREMENT

    1. Physical Quantities, Units & Measurement
    7 Topics
  2. SECTION II: NEWTONIAN MECHANICS
    2. Kinematics
    8 Topics
  3. 3. Dynamics (Forces)
    7 Topics
  4. 4. Mass, Weight & Density
    4 Topics
  5. 5. Turning Effect of Forces
    4 Topics
  6. 6. Energy, Work & Power
    4 Topics
  7. 7. Pressure
    3 Topics
  8. SECTION III: THERMAL PHYSICS
    8. Temperature
    2 Topics
  9. 9. Kinetic Model of Matter
    2 Topics
  10. 10. Transfer of Thermal Energy
    5 Topics
  11. 11. Thermal Properties of Matter
    3 Topics
  12. SECTION IV: WAVES
    12. General Wave Properties
    3 Topics
  13. 13. Light
    7 Topics
  14. 14. Electromagnetic Spectrum
    2 Topics
  15. 15. Sound
    5 Topics
  16. SECTION V: ELECTRICITY & MAGNETISM
    16. Static Electricity
    5 Topics
  17. 17. Current of Electricity
    3 Topics
  18. 18. D.C. Circuits
    2 Topics
  19. 19. Practical Electricity
    4 Topics
  20. 20. Magnetism
    4 Topics
  21. 21. Electromagnetism
    3 Topics
  22. 22. Electromagnetic Induction
    4 Topics
Chapter 3, Topic 1
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Forces

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What is a force?
A force is either a push or a pull that one object exerts on another object.

  • Force is a vector quantity
  • Force = mass ✕ acceleration
  • SI unit of force is Newtons (N) or kg m s⁻²

Different Types of Forces

Contact Forces
Contact forces exist between objects that are in contact.

  • Applied force:
    The push experienced when two objects are pressured together.
  • Normal reaction force:
    The push exerted by a surface on an object pressing on it. (This push is always perpendicular to the surface).
  • Friction:
    A force that opposes motion between surfaces in contact.
  • Tension:
    The pull exerted by a stretched spring, string or rope on an object attached to it.

Non-Contact Forces
Non-contact forces do not require objects to be in contact to exist.

  • Air/water resistance:
    A force that opposes motion due to an object moving in fluid (AKA drag force).
  • Gravitational force/weight:
    The pull exerted by the earth’s gravity on any object.
  • Electric force:
    The attractive or repulsive forces between electric charges.
  • Magnetic force:
    The attractive or repulsive forces between magnets.

Classic Questions of Forces

1. Describe ways in which a force might change the motion of a body.

  • A force is may make stationary bodies move.
  • A force is may moving bodies speed up, slow down or stop.
  • A force is may moving bodies change direction.