Physics Concepts Related to Motion and Forces

Aristotle's Ideas of Motion

• Natural motion: Objects strive to reach their proper place determined by elements (Earth, air, fire).

• Violent motion: Caused by external forces (e.g., wind).

• Law of inertia: An object at rest stays at rest unless acted upon by a force.

• Motion requires force; all claims were later disproven.

Galileo's Contributions

• Disproved Aristotle, showing that objects of different masses fall at the same rate without air resistance.

• Objects need no force to maintain motion in the absence of friction.

Newton's Laws of Motion

• 1st Law (Inertia): An object remains at rest or in uniform motion unless acted on by a net external force.

• 2nd Law: F = ma; acceleration is directly proportional to net force and inversely proportional to mass.

• 3rd Law: For every action, there is an equal and opposite reaction.

Forces

• Defined as pushes or pulls with magnitude and direction.

• Inertia: Resistance to changes in motion; greater mass means greater inertia.

• Equilibrium: Sum of forces in a system is zero (static or dynamic).

Friction

• Acts in the direction opposite to motion; includes static friction (when not sliding) and kinetic friction (when sliding).

• Depends on surface irregularities and contact force.

• Fluid friction includes air resistance, which increases with speed.

Mass and Weight

• Mass: Amount of matter in an object; measures inertia.

• Weight: Gravitational force acting on an object (W = mg).

• Are often confused but are distinct; mass is constant, weight varies with gravity.

Terminal Velocity

• Achieved when air resistance equals gravitational pull, resulting in zero acceleration.

Vector Quantities

• Forces, velocity, and acceleration are vector quantities; they have both magnitude and direction.

• Can be represented graphically using arrows for direction and magnitude.