Notes on Physical Quantities and Forces

Introduction to Physical Quantities

• Physical Quantity:
  • Definition: A measurable property that can be expressed numerically.
  • Examples:
  • Distance
  • Charge
  • Forces
  • Speed
  • Temperature
  • Voltage

Types of Physical Quantities

• Scalar Quantities:

  • Definition: Physical quantities that have magnitude only.
  • Examples:
  • Energy
  • Temperature
  • Mass
  • Distance

• Vector Quantities:

  • Definition: Physical quantities that have both magnitude and direction.
  • Examples:
  • Force
  • Velocity
  • Displacement
  • Acceleration

Forces and Their Characteristics

• Contact Forces:

  • Definition: Forces exerted between two objects that are physically touching.
  • Examples:
  • Pushing or pulling an object.

• Non-Contact Forces:

  • Definition: Forces that act at a distance without direct contact between objects.
  • Examples:
  • Gravitational force
  • Magnetic attraction

Gravitational Field Strength

• Definition:
  • The force acting on an object due to the pull of gravity from a massive object like a planet.
• Gravitational Field Strength:
  • Example Value: 9.81 N/kg (near the Earth's surface)
  • Definition: The gravitational force experienced by a mass of 1 kg is approximately 9.81 N.

Mass and Weight

• Mass:

  • Definition: The amount of matter an object contains.
  • Measurement: Measured in kilograms (kg) or grams (g).

• Weight:

  • Definition: The force exerted by gravity on an object.
  • Measured in newtons (N).
  • Formula:
  • Weight (W) = Mass (m) × Gravitational Field Strength (g)
  • Given as: $W = m \cdot g$

Work Done and Energy

• Work Done:
  • Definition: The amount of energy transferred when a force is applied to move an object.
  • Measurement: Measured in joules (J).
• Example:
  • If a mass is raised, the work done is equal to the gain in potential energy of that mass.

Elastic Materials

• Definition:
  • Materials that return to their original shape after being stretched or compressed.