Physics(Forces on System/Earth's Surface Forces)

9th Grade Physics

Static Equilibrium

When an object is completely still, both the sum of forces and the sum of torques equal zero (Sigma Force and Sigma Torque equal 0).

Torque

The twisting or rotational power of a force. It is calculated by multiplying force by the lever arm (Torque= r x F).

Lever Arm

The perpendicular distance from the pivot point (fulcrum) to where the force is being applied.

Fulcrum

The fixed point, pivot, or axis about which a lever or object rotates.

Line of Action

An imaginary straight line that shows the exact path and direction a force vector is pushing or pulling.

Counterclockwise Torque

A torque that spins an object opposite to a clock's hands, which physics rules consider to be Positive.

Clockwise Torque

A torque that spins an object the same way a clock's hands move, which physics rules consider to be Negative.

Stability

The ability of an object or system to balance and restore itself to its original position after being moved.

Sigma

The greek mathematical symbol that simply means the sum of all forces or torques added together.

Mechanical Weathering

Physically cracking or breaking rock into smaller pieces without changing what minerals the rock is made of.

Chemical Weathering

Breaking down rocks at the atomic level, changing their chemical composition (assisted by electric forces in water).

Abrasion

A type of mechanical weathering where wind, water, or ice wears away rock through friction (like sandpaper).

Weathering

The general natural process of breaking down minerals and solid rocks into smaller pieces.

Oxidation

A type of chemical weathering where oxygen reacts with rock minerals, commonly called "rusting."

Mass Wasting

The downward removal and movement of rock and soil from its location due to the pull of gravity.

Creep

The slowest form of mass wasting, where soil moves downhill so gradually that it is almost imperceptible.

Slump

A specific type of landslide where a large portion of a hill slides downward together as a single mass.

Discharge

The total volume of water that flows past a specific point in a stream or river per unit of time.

Sediment Load

The total amount of solid material (like mud, sand, and pebbles) that a flowing stream carries.

Saltation

The process in wind (Aeolian) systems where sand grains bounce and hop along the surface of the ground.

Deforestation

Clearing away forests, which removes roots that hold dirt in place and causes the loss of 25 billion tons of material annually.

Headline (Promontory)

A rocky point of land that sticks out into the ocean. Waves erode it over time, eventually creating a straighter shoreline.

Wave Erosion (Coastal)

The process where ocean waves wear away rocky headlands and drop that sediment into calmer bays, creating a straighter shoreline over time.

Alpine Glacier

A mountain glacier that moves downward through a slope, carving out a characteristic U-shaped valley.

Continental Glacier

A massive ice sheet covering huge areas of flat bedrock that moves outward in all directions.

Terminal Moraine

A pile of loose sediment and rock debris deposited directly in front of a glacier at its furthest moving point.

Dendritic Stream Pattern

A river drainage pattern that develops in a branching, tree-like shape across the land.

Isostacy

The principle that thicker crust floats deeper in the mantle; if a mountain erodes and gets lighter, the crust rebounds upward.

Plate Tectonics

A constructive geological force driven by Earth's internal heat that moves crust plates and builds mountains.

Rock Cycle

The progression of rocks that we see on the surface of the Earth.