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physics paper 1 > Topic 1: Energy > Flashcards

Topic 1: Energy Flashcards

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1
Q

What is the equation for kinetic energy?

A

Ek= 0.5 x m x v^2

kinetic energy = 0.5 x mass x velocity^2 (speed)

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2
Q

what is kinetic energy ?

A

is the energy stored in moving object

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3
Q

units for kinetic energy

A

kinetic energy - j

mass - kg

velocity - m/s

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4
Q

What is the equation for elastic potential

energy?

A

Ee =0.5 x spring constant x extension^2

Ee = 0.5 x k x e^2

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5
Q

units for elastic potential energy

A

Energy (J)
Spring Constant (N/m)
Extension(m)

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6
Q

What is the equation for gravity potential

energy?

A

Ep = m x g x h

mass x gfs x height

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7
Q

what is gravitational potential energy

A

gravitational potential energy is the energy stored in an object due to its position above the earth surface

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8
Q

units for gravity potential energy

A 
energy = j
mass = kg
gfs = n/kg 
height = m
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9
Q

Define the ‘Specific Heat Capacity’ of a substance.

A

The amount of energy needed to raise
the temperature of 1 kilogram of a
substance by 1 degree Celsius.

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10
Q

What is the definition of ‘Power’?

A

The rate at which energy is transferred

(or rate at which work is done).

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11
Q

State two equations for power. Give SI

units for all quantities involved.

A

power = energy transferred/time

power = work done/time

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12
Q

What is the unit of power?

A

Watt (W)

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13
Q

Two motors lift the same mass through the same
height. Motor A does this in half the time of Motor B.

Which dissipates the most power?

A

Motor A.

The energy transferred is the same but

the time taken is less (P=E/t).

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14
Q

Describe the energy changes involved when a ball is
thrown upwards and then returns to its starting

position. Ignore air resistance.

A

● Upwards: KE is converted to GPE
● Peak: Maximum GPE, zero KE
● Downwards: GPE is converted to KE

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15
Q

Describe the energy transfers for a bungee jumper.

A

● When falling, the GPE is converted to KE of the jumper

● As the cord tightens, KE is converted and
stored as Elastic Potential Energy (EPE)
● At lowest point, the jumper’s initial GPE

equals the EPE stored in the cord

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16
Q

Explain why a bungee jumper slows down once the

cord begins to stretch.

A

● Kinetic energy decreases since it is
converted to elastic potential energy
● Since KE is proportional to (velocity)2,
as KE decreases, so does velocity.

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17
Q

Give examples of chemical energy stores.

A

● Food

● Fuel (eg. wood, coal, petrol)

● Batteries

18
Q

Specific Heat Capacity

A

energy = mass × specific heat capacity × temperature change

19
Q

name the different energy stores

A 
chemical 
kinetic
gravitational potential
elastic potential
thermal
Magnetic
electrostatic
Nuclear
20
Q

Examples of energy changes in a system:

An object thrown (projected) upwards

A

As the ball leaves your hand it has a store of kinetic energy.
At its highest point it has a store of gravitational potential energy (G.P.E).
As you are about to catch it just before it hits your hand it has a
store of kinetic energy.

21
Q

examples of energy changes in a system:

A vehicle slowing down

A

the moving lorry has a store of kinetic energy.
At the brakes are applied the kinetic energy store decreases the energy is transferred to the internal (thermal) energy store in the brakes and the brakes get hot.
You will hear a sound when the brakes of the lorry are applied, the energy of the sound is also transferred to the internal energy store of the surroundings.
When the lorry stops its kinetic energy store is zero.

22
Q

Efficiency - 2 equations

A

efficiency = useful energy output / total energy input

useful power output /
total power

23
Q

the law of conservation of energy

A

energy can be stored, transferred or dissipated - but can not be created or destroyed.

24
Q

The efficiency of a system can be increased by:

A

o Reducing waste output (lubrication, thermal insulation, etc.)
o Recycling waste output (e.g. absorbing thermal waste and recycling as input
energy)

25
Q

Reducing energy waste:

A

Lubrication
o Oil in a motor
o Reduces friction
o So less energy is lost (as heat) through friction

26
Q

Reducing energy waste:

A

Thermal Insulation
o Double Glazing
o Less useful thermal energy lost

so low thermal conductivity

27
Q

insulation

A

have low thermal conductivity such as fibreglass in the loft, foam in wall cavities and trapped gases in double glazing.

28
Q

high thermal conductivity

A

Houses are often built from brick, concrete, wood and glass.

29
Q

reducing thermal energy transfer from a house using high or low thermal conductivity

A

low thermal conductivity

30
Q

Non-renewable

A 
Fossil Fuels (coal, oil,gas)
Nuclear Fuel
31
Q

Renewable

A
  • Biofuel
  • Wind
  • Hydro-electricity
  • Geothermal
  • Tidal
  • Solar
  • Water waves
32
Q

in a closed energy system t

A

there can be transfer of energy but not mass. there is no change to the total energy in the system

33
Q

double glazed windows

cavity walls have a

A

low conductivity

so less thermal energy can pass through

34
Q

What is a renewable energy resource?

A

An energy source that can be

replenished as it is being used up.

35
Q

Give four examples of renewable energy

resources.

A
  1. Wind Energy
  2. Hydro-Electricity
  3. Tidal Energy
  4. Solar Energy
36
Q

Give an example of a non-renewable

energy resource.

A

Fossil fuels (for example coal, oil and

gas).

37
Q

What are the advantages of generating power using

gas rather than coal?

A

Lower emissions of carbon dioxide
Flexible Generation: Gas power
stations have short start-up times so
can be switched on/off more readily

38
Q

State two disadvantages of using

renewable energy resources to generate

power.

A

factors
(like wind speed), so supply is uncertain
more expensive

39
Q

Explain the environmental impacts of burning fossil

fuels.

A

● Carbon Dioxide contributes to the
greenhouse effect, and causes global

warming

● Sulphur Dioxide leads to acid rain, which

can damage buildings and crops

40
Q

Give two reasons for taking repeat readings in an investigation.

A

. calculate a mean
• spot anomalies
• reduce the effect of random errors

physics paper 1 (4 decks)

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