Download When two objects collide, and no other forces act, then conservation

Q1.
(a) When two objects collide, and no other forces act, then conservation of momentum
applies.
(i)
What does the term conservation of momentum mean?
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(2)
(ii)
Apart from collisions and similar events, give another type of event in which
conservation of momentum applies.
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(1)
(iii)
Write, in words, the equation which you need to use to calculate momentum.
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(1)
(iv)
The diagram shows a straight and horizontal runway and two trolleys, X and Y, which
can move on the runway.
X has a mass of 0.2 kg and its velocity is 1.2 m/s to the right. Y has a mass of
0.1 kg and is stationary. When X collides with Y they stick together.
Calculate the velocity of the trolleys after the collision.
Show clearly how you work out your answer and give the unit and direction.
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Velocity of the trolleys = ......................................................................
(5)
(v)
What assumption did you make in order to calculate your answer to part (a)(iv)?
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(1)
Page 1 of 28
(b)
Just before it hits a target, a bullet has a momentum of 5 kg m/s. It takes 0.00125 s for the
target to stop the bullet.
Calculate the force, in newtons, needed to do this.
Write, in words, the equation that you will need to use and show clearly how you work out
your answer.
Force = ................................................ newtons
(3)
(Total 13 marks)
Q2.
The drawing shows a food processor. It has an electric motor. Inside is a blade which spins
round and cuts up the food.
The food processor is designed to transfer electrical energy to kinetic energy. However some of
the energy is wasted as heat and sound.
The power input to the food processor is 1150 W. The power of the spinning blade is 900 W.
(i)
Calculate how much energy is wasted when the food processor is used for two minutes.
Show clearly how you get to your answer and give the unit.
power =
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Energy = .........................................................
(3)
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(ii)
Why does the food processor produce sound when it is switched on?
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(1)
(Total 4 marks)
Q3.
The brick shown in the diagram is being pushed but it is not moving.
(a)
The pushing force does not make the brick move. Explain why.
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(1)
(b)
The weight of the brick does not make it move downwards. Explain why.
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(1)
(c)
A bigger pushing force does make the brick slide across the table.
Write down one thing that the sliding brick will do to the surface of the table.
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(1)
(Total 3 marks)
Page 3 of 28
Q4.
The graph shows how the amount of radiation emitted by a sample of the radionuclide
uranium 238 (U238) changes as time passes.
(a)
What is the half-life of uranium 238 (U238)?
(You should show how you obtained your answer. You may do this on the graph
if you wish.)
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Answer .....................................
(3)
(b)
What fraction (or percentage) of the uranium 238 (U238) atoms will have decayed after
9 billion years?
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(1)
(c)
Uranium 238 (U238) decays through a long series of intermediate radionuclides to stable
atoms of the isotope lead 206 (Pb).
A sample of igneous rock contains 3 atoms of uranium 238 (U238) for every atom of lead
206 (Pb206).
(i)
The intermediate radionuclides are not important when estimating the age of the
rock. Explain why.
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(1)
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(ii)
Estimate the age of the rock.
(You should explain how you obtained your answer.)
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Answer ................................... billion years
(3)
(Total 8 marks)
Q5.
Carefully read the following extract from a safety leaflet. Then answer the questions.
An RCD adaptor is an automatic safety switch. It should be used when there is a
particular risk of electric shock. For example, it is recommended that it is used
with an electric lawnmower.
Inside one make of RCD is an electromagnet that holds the switch closed so that
the RCD is switched on. An electronic circuit in the RCD monitors the difference
between the current in the live wire and the current in the neutral wire.
If something goes wrong and this difference is greater than 30 milliamps then the
RCD will trip (= switch off) within 40 milliseconds.
(a)
Suggest two reasons why there is a particular risk of an electric shock when using an
electric lawnmower.
1. ................................................................................................................................
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2. .................................................................................................................................
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(2)
(b)
Why will there be a difference between the current in the live wire and the current in the
neutral wire if something goes wrong?
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(1)
(c)
(i)
Use the words charge, current and time to write an equation which shows the
relationship between them.
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(1)
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(ii)
Calculate how much charge flows when a current of 30 milliamps passes
for 40 milliseconds.
Clearly show how you get to your answer and give the unit.
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Charge = .....................................................
(3)
(Total 7 marks)
Q6.
A small torch uses a single cell to make the bulb light up.
(a)
The graphs show the voltage across two different types of cell as they transfer the last bit
of their stored energy through the torch bulb.
Describe the differences that the graphs show between the two types of cell.
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(3)
(b)
The diagram shows how bright the torch bulb is for different voltages.
From the point when the voltage of each cell starts to fall, how long will the bulb stay lit:
(i)
with the ordinary cell?
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(ii)
with the nicad cell?
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(4)
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(c)
When the voltage across the bulb falls to half, the current through the bulb falls by
less than half. Why is this?
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(3)
(Total 10 marks)
Q7.
A driver is driving along a road at 30 m/s. The driver suddenly sees a large truck parked
across the road and reacts to the situation by applying the brakes so that a constant braking
force stops the car. The reaction time of the driver is 0.67 seconds, it then takes another 5
seconds for the brakes to bring the car to rest.
(a)
Using the data above, draw a speed-time graph to show the speed of the car from the
instant the truck was seen by the driver until the car stopped.
(5)
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(b)
Calculate the acceleration of the car whilst the brakes are applied.
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Answer = .................................... m/s2
(3)
(c)
The mass of the car is 1500 kg. Calculate the braking force applied to the car.
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Answer = .................................... N
(3)
(d)
The diagrams below show what would happen to a driver in a car crash.
(i)
Explain why the driver tends to be thrown towards the windscreen.
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(ii)
During the collision the front end of the car becomes crumpled and buckled. Use this
information to explain why such a collision is described as “inelastic”.
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(iii)
The car was travelling at 30 m/s immediately before the crash. Calculate the energy
which has to be dissipated as the front of the car crumples.
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(8)
(Total 19 marks)
Q8.
The graph shows how the distance travelled by a car changes with time during a short
journey.
(i)
Describe fully the motion of the car during the first two minutes of the journey.
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(3)
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(ii)
During the last minute of the journey the velocity of the car changes although the speed
remains constant. How is this possible?
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(1)
(Total 4 marks)
Q9.
The first commercial nuclear power station in the world was built at Calder Hall in Cumbria.
(a)
The fuel used at the Calder Hall power station is uranium. Natural uranium consists mainly
of two isotopes: uranium-235
and uranium-238
235 atom is different to that of a uranium-238 atom.
(i)
. The nucleus of a uranium-
Where is the nucleus in an atom?
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(1)
(ii)
Name the two types of particle found in the nucleus.
........................................................... and ........................................................
(2)
(iii)
How is the nucleus of a uranium-238 atom different to the nucleus of a uranium-235
atom?
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(2)
(b)
In the nuclear reactor fission of uranium atoms takes place in reactions such as the one
shown below.
+
+
+ 3(
)
The nuclear reactions are carefully controlled in the power station so that a chain reaction
takes place.
Explain, as fully as you can:
(i)
how fission of uranium atoms takes place in a nuclear reactor;
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(ii)
how this leads to a chain reaction;
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(iii)
why it can be used to generate electricity.
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(4)
(Total 9 marks)
Q10.
The diagram below shows how one type of fuel gauge in a car works. A sliding contact
makes contact with a resistance wire wound in a coil (rheostat). It is connected to a float via a
pivot P. When the petrol level changes the circuit resistance changes. This causes the pointer in
the fuel gauge to move and show how much petrol is in the petrol tank.
The circuit diagram is shown below.
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The petrol gauge is an ammeter. Explain why the reading on the ammeter falls as the
petrol is used.
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(Total 3 marks)
##
The table shows the braking distances for a car at different speeds and kinetic energy. The
braking distance is how far the car travels once the brakes have been applied.
(a)
Braking distance
in m
Speed of car in
m/s
Kinetic energy of
car in kJ
5
10
40
12
15
90
20
20
160
33
25
250
45
30
360
A student suggests, “the braking distance is directly proportional to the kinetic energy.”
(i)
Draw a line graph to test this suggestion.
(3)
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(ii)
Does the graph show that the student’s suggestion was correct or incorrect? Give a
reason for your answer.
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(1)
(iii)
Use your graph and the following equation to predict a braking distance for a speed
of 35 metres per second (m/s). The mass of the car is 800 kilograms (kg). Show
clearly how you obtain your answer.
kinetic energy = ½ mv2
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Braking distance = ........................................ m
(2)
(iv)
State one factor, apart from speed, which would increase the car’s braking distance.
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(1)
(b)
The diagram shows a car before and during a crash test. The car hits the wall at
14 metres per second (m/s) and takes 0.25 seconds (s) to stop.
(i)
Write down the equation which links acceleration, change in velocity and time taken.
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(1)
(ii)
Calculate the deceleration of the car.
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Deceleration = ........................................ m/s2
(1)
Page 13 of 28
(iii)
In an accident the crumple zone at the front of a car collapses progressively. This
increases the time it takes the car to stop. In a front end collision the injury to the car
passengers should be reduced. Explain why. The answer has been started for you.
By increasing the time it takes for the car to stop, the ...................................
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(2)
(Total 11 marks)
Q12.
(a)
What is the principle of conservation of momentum?
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(2)
(b)
The diagram shows a simplified aircraft jet engine.
Adapted from GCSE Physics by Tom Duncan. John Murray (Publishers) Ltd.
(i)
What is the function of the turbine?
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(1)
Page 14 of 28
(ii)
Explain how the engine produces a forward thrust.
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(4)
(c)
During flight, air enters the engine at 175 m/s and leaves at 475 m/s. A forward thrust of
105 kN is produced.
Use the following equation to calculate the mass of air passing through the engine every
second. (Ignore the mass of the burned fuel.)
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Mass of air = ............................................... kg
(2)
(Total 9 marks)
Q13.
The molten rock flowing from an erupting volcano can reach a speed of 8 m/s.
(i)
Write down the equation that links kinetic energy, mass and speed.
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(1)
(ii)
Calculate the kinetic energy of 1 tonne of molten rock flowing at 8 m/s.
(1 tonne = 1000 kg)
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Kinetic energy = ............................................ joules
(1)
(Total 2 marks)
Page 15 of 28
Q14.
Read the information in the box and then answer the questions.
Igneous rocks contain potassium-40. This is a radioactive isotope. It has a
half-life of 1300 million years.
Potassium-40 decays into argon-40 which is stable.
Argon escapes from molten rock. Any argon found in an igneous rock must
have been produced since the rock solidified.
A sample of an igneous rock has one atom of potassium-40 for every three
atoms of argon-40.
(i)
What fraction of the potassium-40 has not yet decayed?
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(1)
(ii)
Calculate the age of the rock.
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Age of rock = .............................................. million years
(1)
(Total 2 marks)
Q15.
(i)
Explain how stars like the Sun were formed.
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(2)
(ii)
The Sun is made mostly of hydrogen. Eventually the hydrogen will be used up and the Sun
will “die”.
Describe what will happen to the Sun from the time the hydrogen is used up until the Sun
“dies”.
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(3)
(Total 5 marks)
Page 16 of 28
M1.
(a)
(i)
either
the momentum in a particular direction after (the collision) is the same as the
momentum in that direction before (the collision)
accept ‘momentum before equals momentum after’ for 1 mark
or total momentum after (the collision) equals the total momentum before
(the collision) (2)
accept ‘momentum before equals momentum after’ for 1 mark
2
(ii)
explosion(s)
or (action of a) rocket (motor(s))
or (action of a) jet (engine)
or firing a gun
accept any other activity in which things move apart as a result of
the release of internal energy eg throwing a ball
1
(iii)
momentum = mass velocity or any correctly transposed version
accept momentum = mass speed
accept p = mv
do not accept momentum = ms
or M = mv
1
(iv)
0.8
if answer 0.8 not given, any two for (1) each:
momentum of X = 0.2 1.2
= momentum of X and Y after impact
= 0.3 v or = (0.1 + 0.2) v
3
m/s
1
to the right
1
(v)
any one from:
conservation of momentum (applies)
no external forces
do not accept just ‘no (other) forces act’
friction is negligible / insignificant
no friction
no air resistance
1
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(b)
force = (change in) momentum ÷ time
or any correctly transposed version
1
4000 or 4 kilonewtons
dependent on correct or no equation
force = 5 ÷ 0.00125 gains 1 mark
2
[13]
M2.
(i)
EITHER
30000 (2) joules/J (1)
or 30 kilojoules/kj
3
OR
power × time = energy
1
time = 120 (seconds)
1
(ii)
vibration (of the food processor / some part of the food processor / the food)
1
[4]
M3.
(a) idea that
balanced by friction force* / pushing force equals
friction force (*note “balanced” by unspecified force)
or
specification of relevant force but no reference to balancing
in both 1(a) and 1(b) gains 1 mark overall
for 1 mark
1
(b)
balanced by upwards force of table*
for 1 mark
1
(c)
makes it (slightly) warm / hot
or
wears it away (slightly) / damages surface
for 1 mark
1
[3]
Page 18 of 28
M4.
(a) indication (in writing or on graph) of finding point where radiation
is halved (e.g. to 24 [from an initial 48]) and relating to the time
difference between the two points
gains 1 mark
but
4.2-4.8*
(*i.e. in this range, including extremes)
gains 2 marks
units billions of years
for 1 mark
3
(b)
¾
or
75%
[allow ecf from (a)]
for 1 mark
1
(c)
(i)
idea that the intermediate nuclides are relatively short-lived
for 1 mark
1
(ii)
idea that ¼ has decayed or ¾ remains
gains 1 mark
but
read graph for radiation level of 36 (stated or shown on graph itself)
gains 2 marks
but
1.6-1.8* (billion years)
(* i.e. in this range, including extremes)
gains 3 marks
3
[8]
M5.
(a)
any two from
(risk of) cutting (through the) cable
accept cutting the wire
grass may be wet
or it may rain
wires may be loose (because cable experiences a lot of movement)
accept cable may be loose
(risk of) touching exposed part(s)
2
(b)
some current will go through (the rest of) the lawnmower / the user / to earth
do not credit any reference to the electromagnet
1
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(c)
(i)
charge = current × time
or any transposed version
accept Q = I × t
or any transposed version
accept C = A × s
or coulombs = amperes × seconds
or any transposed version
or
but only if subsequently used correctly
1
(ii)
EITHER
1200 microcoulombs / μC
or 1.2 millicoulombs / mC
or 0.0012 coulombs /C
3
OR
correct arithmetic
either
converting milliamps to amps
and milliseconds to seconds
or correct multiplication
unit given as coulombs /C
or millicoulombs / mC
or microcoulombs / μC
example : charge = 30 × 40 = 1200 millicoulombs should be
credited with 2 marks
1
[7]
M6.
(a) ordinary cell has higher voltage (normally / at start)
or
ordinary cell 1.3V nicad 1.2V (normally / at start)
for 1 mark
voltage of ordinary cell falls more slowly
gains 1 mark
(accept ordinary cell lasts longer)
but
as above with relevant quantification e.g. falls to zero in 60 seconds
compared to 6 seconds
or
nicad falls to zero 10 times as fast
gains 2 marks
3
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(b)
(i)
answer in range 32-34 (seconds) (inclusive)
gains 1 mark
but
answer in range 22-24 (seconds) (inclusive)
gains 2 marks
(ii)
12 (seconds)
gains 1 mark
but
2 (seconds)
gains 2 marks
4
(c)
resistance of the lamp / filament changes / increases
gains 1 mark
but
resistance of the lamp / filament decreases
gains 2 marks
because the temperature of the filament falls / filament cools
for 1 mark
3
[10]
M7.
(a) Each scale optimum
Else both half size
Straight line joining 30,0 to 30,0.67 to 0, 5.67
any 5 for 1 mark each
5
(b)
6
Else a = 30/5
gets 2 marks
Else a = v/t
gets 1 mark
3
(c)
9000
Else F = 6 × 1500
gets 2 marks
Else F = ma
gets 1 mark
3
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(d)
(i)
Driver has forward momentum
Which is conserved
Giving drive relative forward speed to car
for one mark each
3
(ii)
If inelastic ke lost
Here ke does work crumpling car
for 1 mark each
2
(iii)
Car stops in 75m
gets 1 mark
W = F.d or 9000 × 75
gets 1 mark
W = 675 000 J
OR ke = 1/2 mv2
gets 1 mark
ke = 1/2.1500.302
ke = 675 000 J
3
[19]
M8.
(i)
first statement must be accelerated
if it just accelerated then decelerates award 2 marks
1
final statement must be stationary
1
interim statement decelerates
1
(ii)
direction is changing
1
[4]
M9.
(a)
(i)
centre
1
(ii)
protons and neutrons
2
Page 22 of 28
(iii)
different number of neutrons
gets 1 mark
heavier
gets 1 mark
3 more neutrons or specified numbers
gets 2 marks
2
(b)
atom hit by neutron;
splits into smaller nuclei;
further neutrons released;
neutrons released when one atom splits
cause further fission;
energy released.
any 4 for 1 mark each
4
[9]
M10.
level drops as petrol used;
causes circuit resistance to increase;
causes current to decrease
for 1 mark each
or if change not specified;
(one correct and two vague statements gains 2 marks,
three vague statements gains 1 mark)
e.g. level changes;
)
so resistance changes; ) = 1 mark
so current changes
)
[3]
M11.
(a)
(i)
linear scales used
do not credit if less than half paper used
1
points plotted correctly
all of paper used
1
(straight) line of best fit drawn
allow a tolerance of half square
1
Page 23 of 28
(ii)
correct and straight line through origin
all needed
e.c.f. if their (a)(i) is straight but not through the origin - incorrect
because line does not go through origin
credit a calculation that shows proportionality
1
(iii)
62 ± 0.5 (m)
credit 1 mark for KE = 490000 or 490kJ
credit 1 mark for correct use of graph clearly shown
2
(iv)
any one from: wet or icy or worn or smooth road
accept slippery slope
brakes worn
accept faulty brakes
car heavily loaded
worn tyres
downhill slope
do not accept anything to do with thinking distance e.g. driver tired
or drunk
1
(b)
(i)
acceleration =
accept correct transformation
accept
2
accept m/s =
do not accept acceleration =
1
(ii)
56
accept –56
1
Page 24 of 28
(iii)
deceleration is reduced
accept deceleration is slower
accept acceleration
1
force on car and or passengers is reduced
accept an answer in terms of change in momentum for full credit
1
[11]
M12.
(a)
Total momentum (of a system of bodies) remains constant
accept momentum before (a collision) = momentum after (a
collision)
1
Provided no external force acts
1
(b)
(i)
rotate the compressor
1
(ii)
•
fuel is mixed with the air and ignited
•
causing an increase in the pressure
or temperature or speed of the gases
accept air out faster than air in
accept gases have momentum or
•
force backwards
•
exhaust gases have momentum
(backwards) or force (backwards)
if the answer is in terms of force then this third point must be
scored before the fourth can be credited
•
engine or aircraft has (equal) momentum forwards or force forwards
4
(c)
m = 350
answer 0.35 one mark only
allow one mark if 105 000 or 475-175 or 300 have been used
2
[9]
Page 25 of 28
M13.
(i)
kinetic energy =
accept velocity for speed
accept KE =
mv
2
1
(ii)
32 000
accept 32 kJ
1
[2]
M14.
(i)
accept 0.25 or 25%
1
(ii)
2600
if answer to (c)(i) is ½ then accept 1300
1
[2]
M15.
(i)
from a (giant) cloud of gas or hydrogen
1
condensed or pulled into a smaller volume by gravity
1
(ii)
any three from:
•
fusion decreases or stops
•
collapses rapidly causing the (core) temperature to rise
•
(inward) gravitational forces no longer balance (outward) pressure
•
expands
•
and becomes a red giant
•
it cools
•
then becomes a white dwarf
•
helium may fuse
if the sequence is incorrect deduct [1] therefore maximum 2 marks
3
[5]
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