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Physics - Year 9 revision > Physics Year 9 - Chapter 1 - Conservation and dissipation of energy > Flashcards

Physics Year 9 - Chapter 1 - Conservation and dissipation of energy Flashcards

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1
Q

The specific heat capacity of a substance is the energy needed to …

A

raise the temperature of 1 kg of a substance by 1 degrees

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2
Q

When an object is moved by a force, work is done on the object by the force. So the force ——— to the object.

A

transfers energy

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3
Q

What happens to the energy transferred by a rower in a boat?

A

chemical (body)
mechanical (oars)
friction (water against the boat)

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4
Q

Anything that is moving has energy in its ———- store

A

kinetic energy

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5
Q

Energy can’t be ——– or ————

A

created or destroyed

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6
Q

Describe the changes in energy stores that take place when food is heated in microwave oven.

A

Electrical - makes microwave work
Electrical to cook food
Heat energy comes off the microwave
Light energy and sound waste

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7
Q

Energy is transferred

A

mechanically (by force doing work)
electrically (work done by moving charges)
heating or radiation (eg. light or sound)
waves

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8
Q

Describe the changes in energy store of an electric train as it approaches a station and brakes to a halt

A
  • waste of sound and heat
  • electrical applies the breaks
  • mechanical between the break disks and break pads
  • thermal between break pads and disks
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9
Q

Describe the changes to the energy stores of a ball when it falls and rebounds without regaining its initial height

A
  • gravitational potential energy (up high)
  • as it drops losing gravitational potential but gains kinetic
  • when it hits the ground it has maximum kinetic
  • as it goes up it loses kinetic and gains gravitational but it has gravity and friction working against it so it doesn’t return to its original height.
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10
Q

Force you need to lift up an object = …………………

A

the weight of the object

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11
Q

Energy is never used up. Instead it is —————–

A

just transferred between different energy stores and different objects

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12
Q

When an object falls and gains speed its store of gravitational potential energy DECREASE/INCREASE
and its kinetic energy store DECREASE/INCREASE

A

decrease

increase

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13
Q

Why is the speed of a miner at the bottom of the slide much less than the calculated maximum possible speed?

A
  • Against friction between the miner and slide.
  • Slide isn’t perfectly smooth or miners clothes rough
  • Causes kinetic energy to be transferred as heat
  • loss of air resistance.
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14
Q

Changes in energy transfer of an object when it falls and hits the ground.

A 
- gravitational potential energy store
      GOES TO 
- kinetic energy store
      THEN 
- energy transferred to the surroundings eg. sound waves AND increase in thermal energy stores to surrounds
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15
Q

Hot things have MORE/LESS kinetic energy as they cool down they have MORE/ LESS the average energy of particules.

A

more
lower

Heat energy always goes from a hot body to a cold body.

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16
Q

When a roller coaster gets to the bottom of a descent, describe the energy transfer and changes to energy store that happens

A

As it goes DOWN it gains kinetic energy and when the breaks are applied it becomes heat, sound and mechanical energy.

At the BOTTOM

  • mechanical energy on breaks
  • heat energy, heat from friction
  • sound energy noise from breaks breaking
17
Q

When an object moves down, the energy in its gravitational potential energy store INCREASES/DECREASES

A

decreases

18
Q

Change in energy stores in a candle

A
  • chemical (lighting it)
  • Light (mechanical working)
  • waste energy
19
Q

The work done by a force depends on __________

A

The size of the force and the distanced moved

20
Q

Describe the energy stores of an electric train as it moves UP a hill at a constant speed

A
  • mechanical energy (wheel and track)
  • electrical powers the train
  • gravitational - pushes down on the train
21
Q

A car is brought to a stand still when the driver applies the breaks. Explain why the break pads become warm

A
  • Friction between the break pads and the wheel discs oppose the motion of the wheels
  • Energy is transferred from the kinetic energy store of the vehicle to the thermal energy store of the brake pads and wheel discs
22
Q

A catapult is used to fire an object into the air. Describe the energy transfer when the catapult is
1 stretched
2 released

A
  1. elastic to mechanical (body)

2. elastic to kinetic (the spring is contracting, kinetic is increasing)

23
Q

What happens to the energy transferred by an electric motor used to raise a car park barrier

A

Electrical energy then mechanical as it moves up

24
Q

The greater the mass of an object the SLOWER / FASTER it’s temperature DECREASES / INCREASES when its heated

A

slower

increase

25
Q

Work done to overcome friction is mainly transferred to ________________

A

thermal energy stores by heating

26
Q

Energy is transferred to an object when an object SPEEDS UP/SLOWS DOWN and transferred away from a store when an object SPEEDS UP/SLOWS DOWN

A

speeds up

slows down

27
Q

Change in energy stores in a torch

A
  • chemical energy store in the battery
  • electric current in the wires
  • energy transferred to the surroundings (light waste, increase in thermal energy store of the surroundings)
28
Q

What happens to the energy transfers in a closed system?

A

No energy transfer takes place out of or into the energy store of the system.
Energy can be transferred between energy stores within a closed system

29
Q

Grease is used to reduce friction in a lifting machine. Suggest one effect friction has when two surfaces are rubbed together.

A

heat between surfaces

dissipated into air

30
Q

Describe the energy transfer in a boiling kettle

A
  • Electrical working
  • Thermal energy store of the heating element
  • Heating by particles
  • Thermal energy store of the water
31
Q

Describe the energy transfer of a ball thrown in the air

A
  • chemical energy store of the arm muscles
  • mechanical working
  • kinetic energy store of the arm and the ball
  • mechanical working
  • gravitational potential energy store of the ball
32
Q

Describe the energy transfer of a ball dropped from a height

A
  • gravitational potential energy store of the ball
  • mechanical working
  • kinetic energy store of the ball
33
Q

Describe the energy transfer of a car breaking

A
  • kinetic energy store of the cars wheels
  • -mechanical working
  • Thermal/internal energy store of the tyres
  • heating by particles
  • Thermal/internal energy store of the surroundings
34
Q

Why is the speed of a miner at the bottom of the slide much less than the calculated maximum possible speed.

A
  • Against friction between miner and the slide
  • slide isn’t perfectly smooth or miners clothes rough
  • cause kinetic energy to be transferred as heat/internal energy of surroundings accept lost air resistance

Physics - Year 9 revision (5 decks)

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