# Pre-Physics

## 61 terms · Pre-Physics: Metrics, Motion, Newton's laws, energy, work, simple machines etc.

### standard

In measurement, an exact quantity that everyone agrees upon.

### SI

Modern version of metric system. Based on powers of 10.

### meter

The SI base unit of length

### volume

The amount of space occupied by an object.

### derived unit

Unit of measurement obtained by combining SI units (density= mass/volume)

### liter

Base unit of volume for LIQUID

### mass

The amount of matter in an object

### kilogram

The SI unit for mass

### density

Describes how tighly packed a substance's molecules are.

### time

The interval between two events

### second

The SI unit for time

### kelvin

The SI unit for temperature

### graph

a visual display of information or data

### speed

How fast something is going

### instantaneous speed

The rate of motion at a given instant in time (car speedometer)

### constant speed

speed that does not change

### average speed

A rate of motion determined by= d/t

### velocity

the speed and direction of a moving object

### acceleration

The rate of change in velocity

### force

A push or pull one object exerts on another.

### balanced forces

forces that are equal in size and opposite in direction

### net force

The sum of the forces on an object when unbalanced forces are applied to it.

### inertia

The tendency of an object to resist any change in its motion

### friction

The force that opposes motion between two surfaces that are touching each other

### Newton's Second Law of Motion

An object's acceleration depends on its mass and the Fnet upon it.

### air resistance

frictional force air exerts on a moving object. depends on shape, density, speed, and size

### terminal velocity

the greatest velocity reached by a falling object. Occurs when force of gravity is balanced by air resistance

### projectile

Any object shot of thrown through the air

### centripal acceleration

Acceleration toward the center of a circle by an object moving along a circular path

### centripal force

The force that causes an object moving along a circular path to move toward the center of the path

### momentum

property of any moving object. product of mass and velocity

### law of conservation of momentum

states that the total momentum of a group of objects is conserved unless a net force acts on the objects.

### energy

The ability to cause change.

### kinetic energy

Energy in motion. The greater the mass and velocity, the greater the KE

Stored energy.

### work

The transfer of energy through motion. Measured in JOULES

### mechanical energy

The total amount of KE and PE in a system

### law of conservation of energy

a law stating that energy can form but can't be created nor destroyed under ordinary conditions

### temperature

a measure of the average KE of the particles that make up matter. More KE of particles=higher temp. Less KE= lower temp.

### thermal energy

Total energy of a material's products, including PE and KE

### heat

Thermal energy that flows from warmer material to a cooler material.

### specific heat

The amount of enegy needed to raise 1 kg of material 1 degree.

### machine

a device that makes work easier

### simple machine

a device that accomplishes work with only one movement.

### effort force

the force applied to a machine when a machine is used to do work.

### resistance force

the force exerted by a machine to overcome resistance to gravity or friction.

### ideal machine

A machine in which work input equals work output.

The number of times a machine multiplies the effort force applied to it.

### lever

a simple machine consisting of a bar that is free to rotate around a fixed point.

### fulcrum

The fixed point around which a lever pivots.

### effort arm

The part of a lever on which an effort force is applied.

### resistance arm

The part of a lever that exerts the resistance force.

### pulley

a simple machine consisting of a grooved wheel with a rope or a chain running along the groove.

### wheel and axle

A simple machine consisting of two different sized wheels that rotate together, such as a doorknob or wheel-handled faucet.

### inclined plane

A simple machine consisting of a ramp used to raise objects.

### screw

A simple machine consisting of a special type of inclined plane wrapped in a spiral around a cylindrical post

### wedge

a simple machine consisting of a moving inclined plane with one or two sloping sides. examples are knives and chisels.

### static friction

Static friction is the force between two objects that are not moving relative to each other.

### kinetic friction

Kinetic (or dynamic) friction occurs when two objects are moving relative to each other and rub together

### elastic collision

objects collide and bounce off each other

### inelastic collision

objects collide and stick together