Understanding Types and Effects of Forces

Aug 10, 2024

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Forces Lecture - Miss Todd

Introduction

  • Force: A push, pull, or twisting action on an object.
  • Symbol: F
  • Measurement Unit: Newton (N)
  • Named after Sir Isaac Newton

Representing Forces

  • Arrows represent magnitude (strength) and direction.
  • Forces are vectors (have both magnitude and direction).

Types of Forces

Normal Force

  • Exerted by a surface on an object.

Gravitational Force

  • Attraction between mass and Earth.

Friction

  • Resists motion of objects on a surface.

Applied Force

  • Applied by a person or object to another object.

Pairs of Forces

  • Forces exist in pairs: action and reaction.
  • Balanced Forces: Equal magnitude, opposite direction, no effect.
  • Unbalanced Forces: Different magnitudes, opposite directions, causes movement or change.

Effects of Forces

  • Set an object in motion.
  • Change speed or direction of an object.
  • Change shape of an object.
  • Rotate an object.

Types of Forces

Contact Forces

  • Friction: Surfaces moving over one another.
  • Tension: Pulling action.
  • Compression: Pushing action.

Field (Non-Contact) Forces

  • Gravitational Force: Attraction due to masses.
  • Magnetic Force: Between magnetic objects.
  • Electrostatic Force: Between charged objects.

Gravitational Forces

  • Attractive forces due to mass.
  • Example: Sun and planets in the solar system.
  • Greater mass or closer distance -> stronger gravitational force.

Weight vs. Mass

  • Mass: Amount of matter, measured in kilograms (kg).
  • Weight: Gravitational force, measured in Newtons (N).
  • Mass remains constant; weight changes with location.

Calculating Weight

  • Formula: F_g = m * g
  • F_g: Gravitational force (Newtons)
  • m: Mass (kilograms)
  • g: Gravitational acceleration (9.8 m/s²)

Examples

  1. Car mass = 1485 kg, Weight = 14,553 N
  2. Sammy on Moon: Mass = 70 kg (weight changes, mass doesn't)
  3. Watermelon mass = 2.5 kg, Weight = 24.5 N

Magnetic Force

  • Occurs between magnetic objects.
  • Ferromagnetic Substances: Iron, Nickel, Cobalt.

Types of Magnetic Forces

  • Attraction: Opposite poles (North and South).
  • Repulsion: Same poles (North-North, South-South).

Magnetic Fields

  • Space around a magnet where force is experienced.
  • Earth's magnetic field: From North to South Pole, protects from solar winds.
  • Properties: Imaginary lines, 3D formation, lines never cross, more lines = stronger magnet, lines move North to South.

Electrostatic Forces

  • Exerted by charged objects over a distance.
  • Created by gaining or losing electrons.

Charging Methods

  • Friction: Rubbing objects (e.g., balloon on hair).
  • Conduction: Charged object touches a neutral object.
  • Polarization: Charged object near a neutral object without touching.

Example: Thunder Clouds & Lightning

  • Clouds: Positive on top, negative at bottom.
  • Ground: Positively polarized.
  • Lightning: Discharge of electricity from cloud to ground.

Conclusion

  • This lesson covers the basics of forces and their types.
  • Next section will cover electricity.