Principle of Physical Science Test 2 Cedarville University

Density

important property of materials that measures the compactness of how much mass an object occupies

Density equation

mass/volume

Weight density

weight/volume

pressure

force per unit area that one object exerts on another

Pressure equation

force/area

Pressure in a liquid

force per unit area that a liquid exerts on an something

Effects of water pressure

acts perpendicular to surfaces of a container

independent of shape of container

whatever the shape of a container, pressure at any particular depth is the same

buoyancy

apparent loss of weight of a submerged object

Archimedes' Principle

states that an immersed body (completely or partially) is buoyed up by a force equal to the weight of the fluid it displaces

Apparent weight of a submerged object

weight out of water - buoyant force

displacement rule

a completely submerged object always displaces a volume of liquid equal to its own volume

buoyancy force

equal to the weight of fluid displaced

Which of these blocks submerged in water is the buoyancy force greatest? 1 kg of lead, 1 kg of aluminum or 1 kg of uranium

1 kg of aluminum

Principle of flotation

a floating object displaces a weight of fluid equal to its own weight

gas pressure

a measure of the amount of force per area that a gas exerts against containing walls

gas pressure is proportional to

density

double density of air by

doubling the amount of air and/or decreasing the volume in half

Boyle's Law

relationship between pressure and ideal gases

When you squeeze a party balloon to .8 its volume, the pressure in the balloon

is 1.25 times greater

atmospheric pressure

caused by weight of air

At sea level atmospheric pressure is

101 kPa

Mechanical pump

when the piston is lifted, the intake valve opens and air moves in to fill the empty space

barometer

device to measure atmospheric pressure and elevation

Pascal's Principle

states that a change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid

Continuous Flow

volume of fluid that flows past cross-section of a pipe in a given time is the same as that flowing past other section of the pipe even if the pipe widens or narrows

Bernolli's Principle

states that where the speed of a fluid increases, internal pressure in the fluid decreases

streamlines

thin lines representing fluid motion

laminar flow

smooth steady flow of constant density fluid

turbulent flow

Flow speed above a critical point becomes chaotic

Air speeds up as it is blown across the top of the vertical tube. How does this affect the air pressure in the vertical tube, and what then occurs?

reduced air pressure in the tube (due to Bernoulli) lets atmospheric pressure on the liquid surface push liquid up into the tube where it joins the jet of air in a midst

gas

high speed particles, wide separation of particles, little interaction between particles

liquid

low to medium speed particles, particles near one another, much interaction

Solid

atoms vibrate in solid, atoms near one another, very much interaction (strong)

Celsius scale

zero degrees for freezing point of water to 100 degrees boiling point of water

Fahrenheit scale

32 degrees freezing point of water to 212 degrees for boiling point of water

Kelvin scale

starts at absolute zero (-273 degrees)

kinetic theory of matter

Matter is made up of tiny particles (atoms or molecules) which are always in motion

thermal energy

the total energy (kinetic and potential) of the submicroscopic particles that make up matter

absolute zero

(zero kelvin) lowest limit of temperature

heat

a flow of energy due to a temperature difference

Temperature

a measure of the kinetic energy of a substance

Matter

solid, liquid, vapor (gas); for a given substance, its solid phase is cooler than its liquid phase which is cooler that its vapor phase

joules

scientific applications using metric values

calories

for scientific apps using SAE values

Calories

for counting food calories

1 Calorie

1000 calories

1 calorie

4.19 joules

Thermodynamics

study of the movement of heat (or energy)

Energy

the capacity to do work

first law of thermodynamics

Energy cannot be created or destroyed

second law of thermodynamics

heat does not flow spontaneously from a cool body to a hotter body

Third Law of Thermodynamics

No system can reach absolute zero

Entropy

a measure of the disorder of a system or a measure of the availability of usable energy

specific heat capacity

the quantity of heat required to change the temperature of 1 unit mass of a substance by 1 degree

the high specific heat capacity of water

has higher capacity of storing energy than almost any other substances

thermal expansion

Due to rise in temperature of a substance, molecules jiggle faster and move farther apart.

Most substances expand when heated and contract when cooled.

Expansion of water

Water expands when it turns to ice. Ice has open-structured crystals resulting from strong bonds at certain angles that increase its volume. This make ice less dense than water.

water between 0 degrees C and 4 degrees C

does not expand with temperature

Water at 4 degrees C

smallest volume and greatest density

when 0 degree C water freezes to become ice

largest volume and lowest density

Conduction

transfer of internal energy by electron and molecular collisions within a substance

insulation

Doesn't prevent the flow of internal energy

Slows the rate at which internal energy flows

good conductors

-composed of atoms with "loose" outer electrons

-known as poor insulators

-examples- all metals to varying degrees

poor conductors

-delay the transfer of heat

-known as good insulators

-examples: wood, wool, straw, paper, styrofoam, cork, liquid gases, air or materials with trapped air

Convection

transfer of heat involving only bulk motion of fluids

Why does warm air rise?

Because it is less dense than the surrounding air and is buoyed upward

Radiation

transfer of energy via electromagnetic waves that can travel through empty space

wavelength of radiation

is related to the frequency of vibration

low-frequency vibrations

long waves

high-frequency vibrations

short waves

emissions of radiant energy

every object above absolute zero radiates

net absorber

When a surface absorbs more energy than it emits

net emitter

When a surface emits more energy than it absorbs and temperature tends to fall

Absorption of radiant energy

the ability of a material to absorb and radiate thermal energy is indicated by its color

good absorbers and good emitters

are dark in color

poor absorbers and poor emitters

are reflective or light in color

Reflection of radiant energy

Darkness is often due to the reflection of light back and forth many times partially absorbing with each reflection

Newton's Law of Cooling

Approximately proportional to the temperature difference between the object and its surroundings

greenhouse effect

named for a similar temperature-raising effect in florists' greenhouse

understanding the greenhouse effect requires two concepts

all things radiate at a frequency (and therefore wavelength) that depends on the temperature of the emitting object and glass walls are not transparent for all frequencies of radiation

energy cycle

short wave radiation arrives from the sun and long wave radiation emitted by earth's surface

Destinies of long waves

escape directly to space or be absorbed by gas or dust particles in atmosphere and be reemitted

phases of matter

solid, liquid, gas (and plasma)

Evaporation

change of phase from liquid to gas

Sublimation

form of phase change directly from solid to gas

condensation process

warming process from a gas to a liquid (opposite of evaporation)

boiling process

Rapid evaporation occurs beneath the surface of a liquid

vibration

a wiggle in time

wave

a wiggle in space and time that transports energy

Amplitude

distance from the midpoint to crest or trough

Wavelength

distance from the top of one crest to the top of the next crest or distance between successive identical parts of the waves

period

length of time for one complete vibration

Frequency

number of vibrations per unit of time or the number of waves that passes a point during a unit of time

1 vibration per second

= 1 Hertz

The source of all waves is

vibration

Wave speed

Describes how fast a disturbance moves through a medium

Wave speed equation

frequency x wavelength

Two types of waves

transverse and longitudinal

sound

travels in longitudinal waves- vibrating compressions and rarefactions through air