IGCSE Physics Revision: Unit 1 General Physics & Mechanics | for Cambridge IGCSE 2023 Syllabus

Motion

Definition: Motion refers to the change in position of an object over time, which can be described through various concepts in physics like distance, velocity, and acceleration. It is a fundamental aspect of how objects interact with forces and define the conditions of both static and dynamic scenarios.

Types of Motion:

1. Linear Motion:

   • Definition: This type encompasses motion in which an object moves along a straight line. It can occur in either one-dimensional (straight path) or multi-dimensional (straight in a three-dimensional space) paths.

   • Examples: A car driving straight on a highway or a ball rolling down a straight ramp.

2. Rotational Motion:

   • Definition: It describes motion around an axis, typically involving turning or spinning. Objects exhibiting rotational motion have angular velocity, which is the rate of change of their angular position.

   • Examples: A merry-go-round, earth’s rotation around its axis.

3. Periodic Motion:

   • Definition: This refers to motion that repeats at regular intervals, often predictable and cyclical in nature.

   • Examples: The swinging of a pendulum or the motion of a child on a swing.

Measurement:

• Distance (m): It refers to the total length of the path covered by the object, regardless of direction. It is a scalar quantity and does not depend on the motion path taken.

• Displacement (m): The shortest straight line from the initial position to the final position of the object, often described as a vector quantity because it has both magnitude and direction.

• Time (s):

  • Definition: The duration over which motion occurs. Accurate time measurement is essential in understanding motion and often measured with clocks or stopwatches.

• Speed:

  • Definition: The rate at which an object covers distance. Speed is a scalar quantity, indicating how fast something is moving regardless of direction.

  • Formula: Speed = Distance / Time.

  • Units: Commonly measured in meters per second (m/s).

• Velocity:

  • Definition: Similar to speed, but includes direction; it is a vector quantity.

  • Formula: Velocity = Displacement / Time.

Mass and Weight:

• Mass:

  • Definition: A measure of the amount of matter in an object, which remains constant regardless of location in the universe.

  • Units: Measured in kilograms (kg).

• Weight:

  • Definition: The gravitational force exerted on an object’s mass. It varies depending on the strength of the gravitational field where the object is located.

  • Units: Measured in newtons (N).

  • Formula: Weight (W) = Mass (m) × Gravitational acceleration (g), where on Earth, g is approximately 9.81 m/s².

Density:

• Definition: The mass of an object divided by its volume, providing valuable insight into how much matter is packed into a given space.

• Formula: Density = Mass / Volume.

• Units: Commonly expressed in kg/m³ or g/cm³.

• Significance: Density is crucial in physical science for identifying substances, assessing buoyancy, and understanding properties of materials.

Forces:

• Definition: An interaction that causes an object to change its velocity (either speed or direction) and is a fundamental concept in mechanics. Forces can either be contact or non-contact forces.

Types of Forces:

1. Contact Forces: Require direct physical interaction between objects.

   • Friction: A force that opposes the motion of an object, acting parallel to the contact surface.

   • Tension: A pulling force transmitted through a string, rope, or cable when it is pulled tight.

   • Normal Force: The support force exerted by a surface perpendicular (normal) to the object resting on it.

2. Non-contact Forces: Do not require physical touch to exert influence.

   • Gravitational Force: An attractive force acting between two masses, affecting all objects with mass.

   • Electromagnetic Force: Force described by electric and magnetic fields, responsible for forces between charged particles, which can be attractive or repulsive.

   • Nuclear Force: A strong force that acts between nucleons (protons and neutrons) within an atomic nucleus.

• Units: All forces are measured in newtons (N) as derived from the formula F = m × a (force = mass × acceleration).

Momentum:

• Definition: A measure of the quantity of motion of an object, determined by the product of its mass and velocity. It is a vector quantity, carrying both magnitude and direction.

• Formula: Momentum (p) = Mass × Velocity.

• Units: Measured in kg·m/s.

• Conservation of Momentum: The principle states that in a closed system, the total momentum before an interaction equals the total momentum after the interaction, making it fundamental in collision analysis.

Energy, Work, and Power:

• Energy: The inherent capacity to do work and can exist in various forms such as kinetic, potential, thermal, chemical, and nuclear forms.

• Work: A measure of energy transfer that occurs when an object is moved over a distance by an external force.

  • Formula: Work = Force × Distance × cos(θ), where θ is the angle between the force and the displacement direction.

• Power: The rate at which work is done or energy is transferred over time.

  • Formula: Power = Work / Time.

  • Units: Measured in watts (W), where 1 watt equals 1 joule per second (1 W = 1 J/s).

Pressure:

• Definition: The force distributed over a specified area, fundamental in understanding fluid behavior and various applications in science and engineering.

• Formula: Pressure (P) = Force (F) / Area (A).

• Units: Measured in pascals (Pa), where 1 pascal equals 1 newton per square meter (1 Pa = 1 N/m²).

• Applications: Understanding and calculating pressure is crucial in fields such as fluid mechanics, meteorology, engineering, and many applied science disciplines.