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Question 1

what is the unit for young modulus

Answer 1

Nm-2

Question 2

which property allows steel to be drawn into a wire

Answer 2

ductility

Question 3

which physical property measures the resistance to flow in a fluid

Answer 3

viscosity

Question 4

as the car is passing the lorry the air flow moves the car towards the lorry. explaih why the air flow noves the car towards the lorry

Answer 4

• air flow between the lorry and the car is faster
• air is moving in the opposite direction of the vehicle
• air pressure is decreasing between lorry and the car
• therefore a pressure difference is formed which produces an inward force pulling the vehicle together

Question 5

compare similarites and differences of the elastic and plastic properties of the two materials (steel wire & polythene bag)

Answer 5

• steel wire is malleable so can maintain shape and is stronger
• polythene bag undergos elastic deformation therefore cannot return to original shape once deformed
• both have an elastic section
• both store elastic potential energy that can be released on uloading
hookes law applies to elastic regions of both materials

Question 6

amount of pressure exerted by the gas depends on:

Answer 6

• volume of the container
• the number of gas particles - moles
• temperature of gas

Question 7

ideal gas equation =

Answer 7

pv = nRT

Question 8

what energy transfers are involved in a heating pan of boiling water and why does the temperature of the water not increase

Answer 8

because its an isothermal process the temp of system remains constant
• heat energy is transferred from the fire to the boiling water
• some water molecules are vapourised from liquid into gas which requires energy
• energy supplied by the fire is equal to energy used to vapourise the water molecules
• overall the internal energy of the liquid does not change
• because ^U = O, because ^U = Q -W which rearranges to Q = W

Question 9

aerosols become cold when sprayed why does this happen

Answer 9

no heat is transferred to or from the system. using aerosol is example of adiabatic gas expansion
• expanding aerosol gas works by pushing away the surrounding air
• this requires energy which comes from the internal energy of the aerosol gas
• so aerosol becomes cold when it releases gas

why is this adiabatic?
• no heat was transferred to or from the can to make this process happen
• the only energy transferred was due to the aerosol doing work on the surrounding air because Q = O, ^U = Q-W becomes ^U = -W always negative so temp of gas will decrease

Question 10

1st law of thermodynamics =

Answer 10

sum of all the energy particles in a system is called internal energy and given the symbol U

Question 11

2nd law of thermodynamics =

Answer 11

heat energy never flows spotaneously from a colder object to a hotter object, heat energy always goes from a hotter object to colder.

hand = hotter ice = colder
fire = hotter hand = colder

Question 12

heat pumps and refrigerator and effciency of a fridge

Answer 12

compressor:
• to compress the coolant vapour when it heats up
condenser coils:
• to remove heat energy from the coolant and transfer it to surroundings via conduction + R
• metal coils aid C
• painter black which aids R
• changes from vapour to liquid
expansion device:
• liquid coolant expands and some becomes a vapour, which decreases the temp
• expansion = adiabatic process
evaporator coils:
• to remove heat energy from the fridge by transferring it to the coolant
• energy transferred to the coolant causes it to evaporate and become vapour

Question 13

effciency of a fridge

Answer 13

compressor
~ it heats up when condensing vapour which wastes energy and overall energy
condenser coils
~ effciency of cooling and condensing vapour depends on the differnce in temp between the cooler and the surroundings
~ not all heat/energy can be removed from coolant
expansion device
~ almost 100% effcient
evaporator coils
~ effciency of cooling inside the fridge depends on how fast heat can be extracted from the fridge

Question 14

state one property of modelling clay that shows it is a plastic material

Answer 14

keeps its shape

Question 15

which property allows copper to be hammered into shape

Answer 15

malleability

Question 16

which physical property describes the way some solid materials move slowly and deform permanently with time

Answer 16

creep

Question 17

describe heat engines and how they work

Answer 17

opposite if refrigerators and heat pumps they are devices that use the spotaneous transfer of heat energy from hotter objects to colder objects and convert it to mechanical energy to do work

Question 18

explain the effciency of heat engines

Answer 18

energy effciency measures the proportion of energy which is wasted. this is an important thing to measure and often see stickers on electrical appliances which show how effcient they are.

Question 19

describe the process of petrol engines

Answer 19

1) intake = fuel and air mixture is taken into the piston
2) compression = piston compresses the mixture adiabatically and volume of the mixture decreases and pressure increases
3) ignition = the mixture is ignited and this causes an increase in temperature and pressure with no change in vol
4) expansion = the gas expands adiabatically and works to push the piston out and volume of gas increases and pressure decreases
5) exhaust = the piston is open which decreases the pressure with no change in volume and the gas leaves the piston

Question 20

describe the state of ice

Answer 20

• molecules are close together
• molecules vibrate in a fixed position
• strong IMF between molecules

Question 21

describe water as a state

Answer 21

• molecules are quite close together
• molecules can move by sliding past eachother
• IMF are weaker than ice but stronger than steam

Question 22

describe steam as a state

Answer 22

• molecules are far apart
• molecules are able to move freely
• almost no IMF between molecules

Question 23

melting bouling condensing and freezing

Answer 23

solid to liquid = melting
liquid to gas = boiling
gas to liquid = condensation
liquid to solid = freezing

Question 24

describe the energy of the molecules in each state

Answer 24

• the more energy = the higher temp
• molecules in solid water have least kinetic energy
• molecules in steam gas have most kinetic energy

Question 25

describe the points on the graph

Answer 25

P (solid ice) = molecules held together by strong IMF + molecules gaining energy and vibrating more as temp of ice increases
Q (melting) = energy of molecules stay constant and energy transferred to ice used to break IMF and turn ice into water
R (liquid water) = IMF are weaker than P and Q and molecules can slide over eachother. molecules increase in temp and KE so molecules move faster
S (boiling/vapourisation) = energy of molecules stay constant and energy is transferred to water + used to break IMF + turn water into a gaseous steam
• T (gaseous steam) = IMF are weakest and molecules are able to move freely and molecules are gaining KE and moving faster at a higher temp

Question 26

what is the specific latent heat of vapourisation

Answer 26

energy required to boil one kg of water

Question 27

an object that is heated reaches thermal equillibrium when…

Answer 27

• the energy flowing into the object equals the energy flowing out of the object
• the temp stops increasing and reaches a maximum

Question 28

when an object is heated its temp increases. the thermal capacity of an object is..

Answer 28

• the amount of thermal energy required to increase the temp of the object by 1K

Question 29

explain why honey flows faster on a hot day in comparison to cold day

Answer 29

increase in temp causes a decrease in velocity this is because liquid density decreases and particles flow more easily due to an increase in flow velocity. particles have less collisions this allows liquid to pour at a faster rate in comparison to a cold day

Question 30

give two reasons why this wedge shape allows the car to move as fast as possible

Answer 30

front is aerodynamic giving less friction which reduces turbulance