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Flashcards in Energy Deck (38):
1

Energy is a concept central to all of what?

science

2

a combination of what make up the universe?

matter and energy

3

matter is

substance

4

energy is

abstract, can't be seen, smelled or felt

5

The idea of energy was unknown to who?

Newtron
- existance was debated

6

persons, places and things have energy but we usually observe energy when it is

being transffered or transformed

7

if WORK is to be done what do things must occur

1) Application of force
2) Movement of something by that force
- Displacement must occur for work to occur

8

one joule of work is done when what happens?

a force of 1 newton is exerted over a distance of 1 metre

9

Power is..

the rate at whitch work is being done on an object

10

Power is vector or scalar? What's its unit?

Scalar; Joules/Seconds = Watts (W)

11

One watt of power is expended when what happens?

1 joule of work is done in 1 second

12

typically engines/motors are rated in

horsepower and elctricity in watts

13

1 HP =?

750 Watts (W)

14

Energy can take many forms. Mechanical energy is a form of energy due to (2)

a) the relative position of interacting bodies - Potential Energy (PE)
b) due to their motion - kinetic energy

15

Unit for work and energy

Joules

16

Potential Energy (5)

- an object may store energy because of its postition relative to some other object
- in this stored state it has the potential to do work
- work is required to elevate objects against Earth's gravity - gravitation potential energy
- Gravitation potential energy = weight X height
PE = m(g) X h

17

Kinetic Energy (5)

- one of the kinds of energy into which PE can change into
- can be reffered to as energy of motion
- depends on an object's mass and speed
- can only be 0 or positive
KE = 1/2 m (v^2)

18

Work energy theorem

the work energy theorem states that the work done on a system (net work) equals the energy changes

W = Delta KE
= KE (final) - KE (initial)
= 1/2m (v^2) - 1/2m (v^2)

19

Law of Conservation of Energy

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes

20

In a closed system the total amount of energy at the start is ___ as the total amount of energy at the end

the same

21

Law of Conservation of Energy equation

KE (initial) + PE (initial) = KE (final) + PE (final)
or
KE (initial) + PE (initial)= KE (final) + PE (final) + heat

22

Machines are devices for what?

multiplying forces or simply changing the direction of forces
- every machine is the Conservation of Enery Concpet

23

2 examples of common machines
and how they change direction or multiply the force

- lever - pulley
- by giving up distance

24

Machine lever/pulley equation

(Force X Distance)input = (Force X Distance) output

25

Efficiency

- represents the percent of work put into a machine that is converted to useful work output

26

Efficiency equation

efficiency = (useful energy output) / (total energy input) X 100

27

What would happen in an idea machine?
What happens in reality?

Idea: 100% work input appears as work output
Reality: Doesnt happen because thermal energy is dissipated

28

What is the graveyard of kinetic energy

thermal energy

29

Sources of energy in the world

majority of the world's energy - fossil fuels
- then nuclear
then non-sustainable biomass
- the rest s a mixture of renewable (geothermal, solar, wind etc.)

30

List 5 sources of energy

any of the following
- fossil fuels, geothermal, nuclear fission, solar energy, wind energy, hydroelectric power

31

heat is a type of

energy transfer

32

Kinetic molecular theory (KMT) is based on what assumption?

the assumption that matter is made up of many tiny particles that are always in motion. In a hot body, the particles move faster, and thus have a higher energy than in a cooler body

33

Using the KMT we say temperature is

the average kinetic energy of particles in a material

34

Heat (Q) is

the energy that flows from a substance of hot temp. to a substance of cold temp

35

specific heat capacity (c)

the quantity of heat per unit of mass required to raise the temp by 1 degree celcius.
- every material has its own specific heat capacity
- it is a property of the material

36

Conservation of Energy and Equilibrium

- when two materials transfer heat to each other all the heat that one material gains comes from the heat the other material loses
- when two materials are in contact long enough they will eventually reach thermal equilibrium which means they will have the same temp
- heat will transfer from hot to cold until thermal equilibrium is reached

37

Elastic collision

- a collision in which colliding objects rebound without lasting deformation or the generation of hear
- both momentum and kinetic energy are conserved

38

inelastic collision

a collision in which the colliding objects become distorted, or generate heat and possibly stick together
- momentum is conserved
- kinetic energy is not conserved