Aristotle: Proposed that objects have a natural tendency to move towards their “natural place,” requiring continuous force for horizontal motion. For example, “Falling of the boulders towards the ground and rising of smoke up in the air.”
Galileo: Argued that objects in motion stay in motion unless acted upon by an external force, which was later experimentally verified: “More than 350 years later, it was proven to be correct by an astronomer David Scott in moon.” Galileo also proposed that projectile motion can be analysed in two independent dimensions (horizontal and vertical).
Key Motion Quantities
The sources define and differentiate crucial quantities in mechanics:
Distance: Total path length travelled by an object (scalar).
Displacement: Overall change in position from initial to final point (vector).
Speed: Rate of change of distance (scalar).
Velocity: Rate of change of displacement (vector).
Acceleration: Rate of change of velocity (vector).
Graphical Representation of Motion
The sources emphasise the use of graphs for visualising motion:
Position-Time Graphs: Slope represents velocity.
Velocity-Time Graphs: Slope represents acceleration, area under the curve represents displacement.
Acceleration-Time Graphs: Area under the curve represents change in velocity.
Forces and Free-Body Diagrams
The sources introduce forces, categorising them as:
Fundamental: Gravitational, electromagnetic, strong and weak nuclear forces.
Non-fundamental: Applied force, frictional force, tension force, normal force.
The sources also introduce the concept of free-body diagrams as a tool to visualise forces acting on an object.
Momentum, Impulse, and Collisions
The sources define momentum as “inertia in motion” (p=mv) and explain the law of conservation of momentum, stating that momentum within a closed system remains constant. The sources also discuss different types of collisions:
Elastic Collision: Both momentum and kinetic energy are conserved.
Perfectly Inelastic Collision: Objects stick together after the collision; momentum is conserved, but kinetic energy is not.
Inelastic Collision: Objects bounce off each other; momentum is conserved, but kinetic energy is not.
Overall Observations
The sources offer a comprehensive overview of basic concepts in mechanics. The use of diagrams, examples, and real-world scenarios makes the information accessible and engaging. The historical context helps in appreciating the evolution of scientific thought.