Physical Science Chapter 2

Natural Motion

Natural motion had to do with the nature of bodies.

Violent Motion

Resulted from pushing or pulling forces.

Aristotle believed that natural laws could be understood by logical reasoning.

Two assertions of Aristotle held sway for some 2000 years. One was that heavy objects necessarily fall faster than lighter objects. The other was that moving objects must necessarily have forces exerted on them to keep them moving.

Galileo, who held that experiment was superior to logic in uncovering natural laws.

Galileo demolished the idea that heavy things fall faster than lighter things in his famous Leaning Tower of Pisa experiment, where he allegedly dropped objects of different weights and showed that—except for differences due to the effects of air resistance—they fell to the ground together.

Force

A push or a pull

Inertia

The property by which objects resist changes in motion.

Experiment

Not philosophical speculation, is the test of truth

Mass

A measure of the inertia of a material object. The quantity of matter in an object. It is also the measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way.

Weight

The force upon an object due to gravity

Kilogram

The standard unit of mass

Newton

The scientific unit of force

Net Force

The combination of all forces acting on an object.

Vector quantity

A quantity whose description requires both magnitude and direction.

Tension

Stretching force

Mechanical Equilibrium.

When the net force on something is zero.

Equilibrium Rule

The vector sum of forces acting on a non accelerating object equals zero.

Support force

The force that supports an object against gravity; often called the normal force.

Friction

A force that opposes motion or attempted motion

Air Resistence

The force of friction acting on an object due to its motion through air.

Instantaneous Speed

The speed at any given instant

Average Speed

Total Distance covered divided by total time.

Acceleration

The rate at which velocity changes with time