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Define energy

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Physics

8th

59 Terms

1

Define energy

The ability to do work

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2

Define work

Measure of energy transfer when an object is moved

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3

For work to be done...

Work is done when a force applied to an object causes the object to move in the same direction as the force applied

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4

Define power

The rate at which work is done

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5

What units do we do for energy?

Joules (J)

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6

What units do we use for power?

Watts

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7

How do you convert joules to kilojoules?

Kj = J/1000

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8

How do you convert kilojoules to joules?

J = Kj x 1000

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9

What is the formula for work?

Work = force x distance

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10

What is the formula for power?

Power = work/time

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11

What is potential energy?

Potential energy is stored energy. It is energy that could make work happen.

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12

What is kinetic energy?

The energy of an object due to its motion. Involves a movement

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13

What are examples of potential energy?

  • gravitational potential energy

  • chemical potential energy

  • nuclear potential energy

  • elastic potential energy

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14

What is elastic energy? (give examples)

Energy stored in objects that can be stretched, compressed or bent. When released, they go back to their original form. e.g. rubber band, bouncy ball

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15

What increases the amount of elastic energy of an object?

How stretched, compressed or bent an object is - the more stretched, compressed or bent, the more elastic potential energy.

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16

Why is elastic energy considered potential energy?

Because it could lead to work happening but it hasn't happened yet.

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17

What is gravitational energy? (give examples)

The energy of an object stored in its position above the earth. e.g. a bolder at the top of a hill, a child at the top of a slide

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18

When do objects have gravitational energy?

Objects have gravitational potential energy when they could be pulled down due to gravity

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19

What factors affect the amount of gravitational energy in an object?

The height - the higher the object, the more GPE The mass - the heavier the object, the more GPE

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20

Why is gravitational energy considered potential energy?

Because objects have stored energy due to their height above the earth, which could lead to work happening due to gravity

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21

What is nuclear energy?

Energy stored in the nucleus of the atom. It is within the strong bond that holds the nucleus together.

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22

Why is nuclear energy considered potential energy?

Because it is stored energy that can be transformed into kinetic energy leading to work. (Usually transferred into heat/thermal energy)

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23

What is a nuclear reaction?

There are two types: fission = 1 nucleus is split in 2 fusion = 2 nuclei are smashed together

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24

Why is a nuclear reaction considered a chain reaction?

As one nucleus breaks it releases particles which fly off and into other atoms, causing their nuclei's to break.

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25

What is chemical energy? (give examples)

Energy stored in bonds between atoms. Found between atoms. e.g. fuels, food, batteries

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26

Why is chemical energy considered potential energy?

Because it is energy that is stored and is not working yet but could lead to work when transformed.

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27

How do our bodies use stored chemical energy from food and convert it?

Organisms ‘run on’ Chemical energy: cells break apart the bonds between atoms to use it. Fats and oils are made up of long chains of atoms = lots of bonds = lots of energy

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28

What is sound energy?

Energy produced by the vibration of particles

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29

How does sound energy travel?

Sound moves in longitudinal/compressional waves. the vibration is transferred from particle to particle in all directions. The particles vibrate back and forth, however they stay in the same spot.

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30

Why is sound energy considered kinetic energy?

Because it involves the movement of particles.

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31

Why can sound not travel in a vacuum?

Sound travels by vibrating particles. If there are no particles to vibrate, it can not travel. There are no air particles in a vacuum so sound cannot travel.

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32

What happens to a sound wave when it comes into contact with a hard, solid surface?

It is reflected and bounces back towards the source. This is the cause of echoes.

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33

What happens to a sound wave when it comes into contact with a soft surface?

It is absorbed and sound energy is transferred into thermal energy in the material. Less sound comes back to the source.

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34

What happens to a sound wave when it comes into contact with a rough, uneven surface?

It is diffused and the sound is reflected back in all different directions. The sound is muffled.

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35

How fast does sound travel through different states of matter?

Solid = fastest Liquid = middle Gas = slowest

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36

Why does sound travel differently through different states of matter?

Sound moves the quickest in solids because the particles are tightly compacted and therefore each particle can easily transfer vibrations to neighbouring particles.

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37

What is light energy?

A type of energy that moves through electric and magnetic fields.

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38

How does light energy travel?

Light travels as a wave through electric and magnetic fields. It DOES NOT NEED PARTICLES.

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39

Why is light energy considered kinetic?

Because it involves the motion of waves through the elecric and magnetic fields.

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40

What speed does light travel?

300 000 000 m/s

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41

What is the electromagnetic spectrum?

The complete range of radiation released from the sun. It is the range of wavelengths that electromagnetic radiation contains.

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42

What are the waves of the electromagnetic spectrum from smallest to largest?

SMALLEST Gamma X-ray Ultraviolet Visible light Infrared Microwaves Radiowaves LARGEST

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43

What is the difference of waves between colours?

Red light is the biggest in wave size = small bending Violet light is the smallest in wave size = large bending

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44

What is reflection?

A change in direction of a light wave as it bounces off a surface

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45

What is refraction?

The bending of light as it enters or leaves a material

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46

What is dispersion?

The splitting of white light into the different colours of the visible light spectrum

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47

What happens when light hits a transparent material?

All light is transmitted through and a clear image can be seen through the substance

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48

What happens when light hits a translucent material?

Some light is reflected and some light passes through but is scattered. A fuzzy image can be seen through the substance.

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49

What happens when light hits an opaque material?

Light is either reflected or absorbed - no light is transmitted. No image can be seen through the substance.

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50

What does transmitted mean?

e.g. if light is transmitted it goes through the material

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51

What is electrical energy?

Energy caused by the movement of electrons from atom to atom. Movement of electrons in a current (flow in one direction)

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52

Why is electrical energy considered kinetic energy?

Because it involves the movement of electrons from one atom to another.

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53

What is thermal energy?

The total movement of particles in an object

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54

Why is thermal energy considered kinetic energy/

Because it involves the movement of particles or waves

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55

What is the difference between heat and temperature?

Temperature is the measure of the average kinetic energy of the particles in an object. It tells us how hot or cold something is. Heat is the transfer of thermal energy from object to object.

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56

What direction does thermal energy move in?

From hot to cold. Thermal energy moves from the object with the higher kinetic energy to the object with lower

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57

What is conduction?

The transfer of thermal energy from one particle of matter to another via direct particle to particle contact. Heat transferred through collision of particles. As particles with higher kinetic energy come in contact with particles with lower kinetic energy, the energy is transferred, making them vibrate faster.

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58

What is convection?

The transfer of thermal energy through the bulk movement fo matter. Non contact, liquids and gases. Energy transferred through bulk movements due to density differences. Heated, less dense particles rise, and cooler, less dense particles fall.

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59

What is radiation?

The transfer of thermal energy by electromagnetic waves. Doesn't require particles - moves as waves through electromagnetic radiation. Moves in all directions and can travel through space.

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