Download P2_Key Recall Questions

P2 Physics
Additional Science
Key Recall
Questions
*Cover up the answers, ask yourself a question (or get your partner to ask you), if you get it
right then tick the chart, wrong put a cross. Keep practising until all columns are ticked!
P2.1 Forces and their effects_1
Key Recall Question
1. How are forces represented?
2. What is a resultant force?
3. What will happen if the resultant force acting on a
stationary object is zero?
4. What will happen if the resultant force acting on a
stationary object is not zero?
5. What will happen if the resultant force acting on a
moving object is zero?
6. What will happen if the resultant force acting on a
moving object is not zero?
7. What is the unit for force?
8. How are force, mass and acceleration linked?
9. What are the units of mass?
10. What is the unit of acceleration?
Answer
By an arrow, ideally from where the force
originates
A single force which replaces a number of forces all
acting at a particular point. The resultant force has
the same effect on the motion as all the forces
acting together.
The object will stay stationary.
The object will accelerate in the direction of the
resultant force.
The object will move at the same speed and in the
same direction.
The object will accelerate in the direction of the
resultant force.
Newtons (N)
Force = mass x acceleration
F(N) = m (kg) x (m/s2)
Kilograms (kg), grams (g) or sometimes tonnes
(1000kg)
Metres per second squared (m/s2)
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P2.1 Forces and their effects_2
Key Recall Question
1. What does the gradient of a distance-time graph
represent?
2. What are the units of speed (velocity)?
3. What does a horizontal line on a distance-time
graph represent?
4. How do you calculate the speed (velocity) from a
distance-time graph?
5. What is the difference between speed and
velocity?
6. What does the gradient of a velocity-time graph
represent?
7. What are the units for acceleration?
8. What does a horizontal line on a velocity-time
graph represent?
9. How do you calculate the acceleration from a
velocity-time graph?
10. How do you calculate the distance from a
velocity-time graph?
Answer
Constant speed (velocity)
Metres per second (m/s) or kilometres per hour
(km/hr). NOTE; miles per hour is not an SI unit.
The object is stationary.
Speed (velocity) is distance/time so use the axis to
find the distance travelled and divide it by the time
taken.
The velocity of an object is its speed in a given
direction.
Acceleration.
metres per second squared (m/s2)
The object is moving at a constant velocity.
Use a = v-u
t
Where a = acceleration (m/s2), v = final velocity
(m/s), u = initial velocity (m/s) and t = time (s)
Work out the area underneath the graph. The
answer will be in metres (m).
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P2.1 Forces and their effects_3
Key Recall Question
1. What happens to the forces when a vehicle travels
at a steady speed?
2. Which force are most of the resistive forces acting
on a vehicle caused by?
3. How is the braking force affected by speed?
4. What is ‘stopping distance’?
5. What three things can a driver’s reaction time be
affected by?
6. What happens to the temperature of the brakes
when you apply them and why?
7. What can braking distance be affected by?
8. If an object moves through a fluid (liquid or gas)
faster, what happens to the frictional force?
9. Why does a falling object initially accelerate?
10. What will eventually happen to the resultant
force of a falling object?
11. What is ‘terminal velocity’?
Answer
The resistive forces balance the driving force
Air resistance.
The bigger the speed the greater the braking force
required to stop it in a certain distance.
The distance the driver travels during the driver’s
reaction time (thinking distance) and the distance
it travels under the braking force (braking
distance).
Tiredness, drugs and alcohol.
It increases because the work done by the friction
force between the brakes and the wheel reduces
the kinetic energy of the vehicle so the
temperature of the brakes increases.
Poor weather (icy and wet conditions) and poor
condition of the vehicle (tyres or brakes).
It will increase
Due to the force of gravity
It will be zero
The speed (velocity) an object reaches when the
resultant forces are zero. It is measured in m/s
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P2.1 Forces and their effects_4
Key Recall Question
1. How do you calculate the weight of an object?
2. What will happen to a spring when a force is
applied?
3. What type of energy is stored in a spring when it is
stretched?
4. What is the extension for an elastic object
directionally proportional to?
5. What is the limit of proportionality?
6. In F = k x e, what does e represent?
7. In F = k x e, what does k represent?
8. What are the units for ‘spring constant’?
9. If a spring has a spring constant of 3 and it is
extended by 0.1 m, what is the Force applied to
produced this extension?
Answer
Mass(kg) x gravity (N/kg) = Weight (N)
It will change shape and stretch
Elastic potential energy
The force applied
The point at which the force applied and extension
is no longer proportional
The extension in metres.
The spring constant
Newtons per metre (N/m)
F=k x e
F = 3 x 0.1
F = 0.3 N
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P2.2 The kinetic energy of objects speeding up or slowing down_1
Key Recall Question
1. What is ‘work done’?
2. What is the unit for work done?
3. What is transferred when work is done on
an object?
4. Will the amount of work done to move an
object across ice be smaller or greater than to
move the same object, the same distance
across grass?
5. What is ‘Power’ and what are its units?
6. What is gravitational potential energy?
7. What are the units for gravitational field
strength (g)?
8. If the gravitational field strength on Earth is
10 N/kg what is the weight of someone who
has a mass of 70 kg?
9. If the person in question 8 stood on a stool
which is 1m high, what would their
gravitational potential energy be?
Answer
When a Force causes an object to move through a
distance. W = F (N) x d (m)
Joules (J)
Energy
It will be smaller because there are less frictional forces to
counteract.
The work done or energy transferred in a given time.
P = E/t. The units for Power are Watts (W), Energy are
joules (J) and time is seconds (s)
The energy that an object has due to its position in a
gravitational field. Ep = m x g x h
Where Ep is the change in gravitational potential energy in
joules (J), m is the mass in kilograms (kg), g is the
gravitational field strength in newtons per kilogram (N/kg)
and h is the change in height in metres (m)
N/kg
70 kg x 10 N/kg = 700 N
(weight = m x g)
Ep = m x g x h
Ep = 70 x 10 x 1
Ep = 70 J
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P2.2 The kinetic energy of objects speeding up or slowing down_2
Key Recall Question
1. What two factors does the kinetic energy of an
object depend on?
2. How can the kinetic energy equation be rearranged
to calculate speed?
3. What must an object be doing in order to have
momentum?
4. What is the equation for calculating momentum?
5. How does the momentum of an object before a
collision or explosion compare to the momentum after
a collision (assuming it is a closed system)?
6. What are the units for momentum?
7. If an object has a momentum of 30 kg m/s and it
collides into another object and sticks to it, what will
the momentum of the two objects be?
8. The mass of the two objects in question 7 is 10 kg.
What will the velocity of the objects be?
9. When a cannon is fired it often moves backwards.
What is this backward movement called?
10. How can the momentum of the recoil of a gun be
the same as the momentum of the bullet, but the
person firing the gun is not injured?
11. If two ice skaters, of mass 60 kg and 90 kg, are
standing in the middle of an ice rink and they push
against each other, which ice skater will move with the
greatest velocity?
Answer
Mass and speed. Ek = ½ x m x v2
V = 2 x Ek
M
Moving
p=m x v
p is momentum in kilogram metres per second (kg m/s), m
is mass in kilograms (kg) and v is velocity in metres per
second (m/s)
It is equal
kg m/s
30 kg m/s
v = p/m, v = 30/10 so v = 3 m/s
Recoil
Because the mass of the bullet is much smaller than the
mass of the gun. Therefore the velocity of the bullet can
be much greater than the velocity of the gun, thus making
the momentum of the two objects the same.
The 60 kg ice skater because to equal the momentum of
the other ice skater (p = m x v) they must have a greater
velocity.
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P2.3 Currents in electrical circuits_1
Key Recall Question
1. What happens when insulating materials
are rubbed against each other?
2. What particle is rubbed off between each
insulating material when they are rubbed
together?
3. How does one of the insulating materials
become negatively charged?
4. How does one of the insulating materials
become positively charged?
5. What happens if two electrically charged
objects are brought together?
6. If two electrically charged materials, which
carry the same charge, are brought near to
each other what will happen?
7. If two electrically charged materials, which
carry different charges, are brought near to
each other what will happen?
8. What sort of materials can electrical
charges move through easily?
9. What is electric current?
10. What does the size of electric current
depend on?
11. How can the size of current be calculated?
Answer
They become electrically charged.
Electrons (which have negative charges)
It gains electrons (from the other insulating material)
It loses electrons (to the other insulating material)
They exert a force on each other (e.g. a charged balloon
near to charged hair)
They will repel each other.
They will attract each other.
Metals (think back to chemistry and their structure to
understand why)
The flow of electric charge.
The rate of flow of electric charge.
I = Q/t
where I is current in amperes (A), Q is the charge in
coulombs (C) and t is the time in seconds (s).
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P2.3 Currents in electrical circuits_2
Key Recall Question
Answer
1. What is the potential difference (voltage)
between two points in an electric circuit?
2. How can potential difference be calculated?
3. What do these circuit symbols represent?
The work done (energy transferred) per coulomb of
charge that passes between the points.
V = W/Q
where V is the potential difference in volts (V), W is the
work done in joules (J) and Q is the charge in coulombds
(C)
Open switch, closed switch, lamp and fuse
4. What do these circuit symbols represent?
Cell, battery, resistor and voltmeter
5. What do these circuit symbols represent?
Ammeter, light dependent resistor (LDR), variable
resistor and thermistor
6. What do these circuit symbols represent?
Light emitting diode (LED), light dependent resistor (LDR)
and diode.
7. What are current-potential difference graphs
used for?
8. What does the current-potential difference
graph for a resistor at constant temperature
look like?
9. What is the current through a resistor (at a
constant temperature) directly proportional to?
They show how the current through a component varies
with the potential difference across it.
A straight diagonal line going through the point of origin.
Potential difference across the resistor.
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P2.3 Currents in electrical circuits_3
Key Recall Question
1. How can the resistance of a component be
found out?
2. How can current, potential difference and
resistance be calculated?
3. If a component has a resistance of 10  and a
current of 2 A is passing through it, what will be
the potential difference?
4. If a component, which has a larger resistance
than the component in question 3, is placed in
the circuit, what will happen to the current?
5. How do you work out the potential difference
of four 3 V cells connected in series?
6. If one of the cells in question 5 was connected
a different way around, what would the potential
difference be?
7. When three 2  resistors are place in series,
how can you calculate the total resistance?
8. If a lamp, resistor and fuse (which all have
different resistance) are connected in series,
what do we know about the current in each
component.
9. What is the total potential difference across
all of the components in question 8 if the
potential difference from the power supply is 30
V?
Answer
By measuring the current through it and the potential
difference across it.
V=IXR
Where V is the voltage in volts (V), I is the current in
amperes (A) and R is the resistance in ohms (.
20 V
It will be smaller.
The potential difference is the sum of the potential
difference of each cell so 3 + 3 + 3 + 3 = 12 V
0 V (no current will flow)
Total resistance is the sum of the resistance in each
component so 2 + 2 + 2 = 6 
It will be the same.
30 V (because the total potential difference of the
supply is shared across all components in a parallel
circuit)
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P2.3 Currents in electrical circuits_4
Key Recall Question
Answer
1. If components are connected in a parallel
circuit what do we know about the potential
difference?
2. If there is a 20 V cell and two lamps (with
different resistance) connected in parallel to the
cell, what would the potential difference across
each lamp be?
3. If the current through lamp in the first branch
of the circuit is 4 A and the second branch is 10 A,
what is the total current in the whole circuit?
4. Which component does this current-potential
difference graph represent and why?
The potential difference across each component is the
same.
5. Can you explain ‘resistance’?
An electric current flows when electrons move through
conductors. As they move through the conductor they
collide with ions, this collision between electron and
ion in the conductor is what causes resistance.
Electrons collide with ions more frequently (as there
are more ions for them to collide with)
Because there are fewer electrons to carry the current
in a thin wire and these will collide with the ions.
6. Why does increasing the length of a wire
increase resistance?
7. Why does a thin wire have a higher resistance
than a thick wire?
20 V across each lamp
The total current in a parallel circuit is the sum of the
currents through the separate components so 10 + 4 =
14 A
A filament bulb because the graph shows that the
resistance of the filament bulb increases as the
temperature of the bulb increases.
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P2.3 Currents in electrical circuits_5
Key Recall Question
Answer
1. What component does this graph represent
and why?
A diode, because it shows current only flowing in one
direction, the diode has a very high resistance in the
reverse direction.
2. How do Light Emitting Diodes (LEDs) work?
They only emit light when current flows through in the
forward direction.
Because they use a much smaller current than other
forms of lighting.
In small lights (e.g torches) and indicator lights in
electrical equipment (e.g. computers and TVs)
The resistance decreases as light intensity increases.
3. Why are LEDs becoming more popular?
4. Can you give an example of how LEDs are
used?
5. How does the resistance of a light dependent
resistor (LDR) vary with light intensity?
6. Can you give an example of how LDRs might
be used?
7. How does the resistance of a thermistor vary
as temperature increases?
8. Can you give an example of how thermistors
might be used?
9. Can you explain how a thermistor in a fire
alarm might work?
To switch lights on when it starts to get dark.
The resistance decreases.
In thermostats which regulate central heating and fire
alarms.
As the temperature increases, the resistance in the
thermistor decreases so current flows. This allows
current to flow around the circuit to sound the alarm.
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P2.4 Using mains electricity safely and the power of electrical appliances_1
Key Recall Question
Answer
1. What is direct current (d.c.)?
2. What sorts of power supplies produce
direct current?
3. What is alternating current (a.c.)?
4. What sort of power supplies produce
alternating current?
5. What sort of electricity is represented by
this oscilloscope trace?
Current that always passes in the same direction.
Cells and batteries.
6. If the above oscilloscope trace represents 1
second, what is the frequency of the supply?
7. What is the frequency and potential
difference of mains electricity?
8. How are most electrical appliances
connected to mains electricity?
9. Which two wires are always found in
electrical cables?
10. Which third wire is often found in
electrical cables?
11. Why do some wires not have an Earth
wire?
2 cycles per second (hertz)
Current which is constantly changing direction.
Main electricity.
a.c.
50 hertz and 230 V (approx)
Using cable and three pin plugs.
Live and neutral
Earth
Because the appliance they are attached to have plastic
casing (double insulated) or the live wire cannot touch the
casing. Therefore they cannot cause electric shocks.
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P2.4 Using mains electricity safely and the power of electrical appliances_2
Key Recall Question
1. What are mains electricity cables made
from and why?
2. What colour is the neutral wire?
3. What colour is the Earth wire?
4. What colour is the live wire?
5. What are the pins in an electric plug made
of and why?
6. How are the three wires in the cable wired
up in the three pin plug?
7. What is the role of a fuse in the plug?
8. If a device works at 4 A, should there be a 3
A, 5 A or 13 A fuse in the plug?
9. Simply, how do residual current circuit
breakers (RCCB) work?
10. What is the advantage of an RCCB over a
fuse?
11. Why are some appliances with metal
casings ‘earthed’?
Answer
The outside layer is made from plastic because it is a good,
flexible insulator so should not give electric shocks. The
two or three wires inside are made from copper as they
are good conductors.
Blue
Green and yellow stripes
Brown
Brass, because they are good conductors.
Blue goes left, brown goes right, striped goes to the top.
The fuse is connected to the live wire so if the current gets
too high the fuse will melt and disconnect the circuit.
A 5 A (the fuse which is closest to the current in the device
but above it)
They detect a difference between the current in the live
wire and the neutral wires.
They work much faster.
Because the earth wire is connected to the metal casing so
should the live wire touch the casing, the electricity has a
safe route to pass through the earth wire and not cause
electric shock.
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P2.4 Using mains electricity safely and the power of electrical appliances_3
Key Recall Question
1. What happens to a resistor when an
electrical charge flows through it?
2. What advantages do power saving lamps
such as Compact Fluorescent Lamps (CFLs)
have over filament bulbs?
3. What do you call the rate at which energy
is transferred in an appliance?
4. How do you calculate the rate at which
energy is transferred in an appliance?
5. If a lamp transfers 2000 J in 10 seconds
what is its power?
6. Which equation links power, potential
difference and current?
7. If an appliance has a power of 2.3 kW and
the potential difference of 230 V, what is its
current?
8. Would a 3 A, 5 A or 15 A fuse be most
suitable for the appliance in question 7?
9. How are energy transferred, potential
difference and charge related?
Answer
It gets hot
They waste less energy through heat so that are more
efficient and cost less to run.
Power
P = E/t
Where P is power in watts (W), E is energy in joules (J) and
t is time in seconds (s)
P = E/t
P = 2000/10 = 200 W
P=IXV
Where P is power in watts (W), I is current in amperes (A)
and V is potential difference in volts (V)
P = I X V so I = P/V (remember 1 kW = 1000 W)
I = 2300/230
I = 10 A
13 A
E=VXQ
Where E is energy in joules (J), V is potential difference in
volts (V) and Q is charge in coulombs (C).
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P2.5 What happens when radioactive substances decay and the uses and dangers of their
emissions_1
Key Recall Question
Answer
1. What does the nuclear model of the atom
look like?
2. Which scientists used scattering
experiments to help discover the nuclear
model of the atom and change scientists from
thinking about the ‘plum pudding’ model?
3. According to the nuclear model, what is
most of the atom?
4. What are the relative masses and charges
of protons, neutrons and electrons?
The atom consists of a small central nucleus composed of
protons and neutrons surrounded by electrons.
Rutherford and Marsden
5. What is important about the numbers of
electrons and protons in an atom?
6. What do atoms gain or lose to form ions?
7. What is an isotope?
8. What is the atomic number?
9. What is the mass number?
10. Why are some substances radioactive?
Empty space
Proton; mass = 1 and charge = +1
Neutron; mass = 1 and charge = 0
Electron; mass = negligible and charge = -1
They are equal so the atom has no overall charge.
Electrons.
An atom which has different numbers of neutrons (the
atom always has the same number of protons and
electrons)
The total number of protons in an atom.
The total number of protons and neutrons in the atom.
Because they give out radiation from their nuclei all of the
time, whatever happens to them.
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P2.5 What happens when radioactive substances decay and the uses and dangers of their
emissions_2
Key Recall Question
1. Where does background radiation come
from?
2. What are the three types of radiation
emitted by a radioactive substance?
3. What is alpha radiation?
4. What is beta radiation?
5. What is gamma radiation?
6. Radon (atomic number 86, mass number
219) decays to polonium by releasing an alpha
particle. What is the atomic number and mass
number of polonium?
7. Which type of radiation is the most
penetrating?
7. Which type of radiation can be stopped by
a sheet of paper?
8. Which type of radiation is only stopped by
many centimetres of lead?
9. What can stop beta radiation?
10. Which two types of radiation are
deflected by electric and magnetic fields and
why?
11. Which type of radiation is most ionising?
Answer
Natural sources (e.g. rocks and cosmic rays from space)
and man-made sources (e.g. fallout from nuclear weapons
tests and nuclear accidents)
Alpha, beta and gamma.
Two neutrons and two protons (a helium nucleus)
A (high energy) electron from the nucleus
Electromagnetic radiation
Atomic number = 84 and mass number = 215. (because an
alpha particle has two neutrons and two protons)
Gamma
Alpha
Gamma
Aluminium
Alpha and beta, because they consist of charged particles.
Alpha (ionisation means it can knock electrons off atoms,
particularly problematic if this happens to atoms in DNA as
it can lead to cancer)
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P2.5 What happens when radioactive substances decay and the uses and dangers of their
emissions_2
Key Recall Question
1. If a radioactive substance is absorbed
inside the body, which is most dangerous and
why?
2. Which is the most dangerous radioactive
source outside the body and why?
3. Can you give some examples of how
radiation is used?
Answer
Alpha because it is the most ionising and easily absorbed
by cells (beta and gamma are not easily absorbed)
Beta and gamma because they are the most penetrating
(alpha is not likely to reach cells inside)
Smoke detectors, sterilising equipment, killing cancer cells,
dating rocks, chemical tracers in medicine and measuring
the thickness of materials in industry.
4. Which types of radiation is most likely to be Beta and gamma, because they are less likely to be
used as a medical tracer and why?
absorbed by cells so more likely to pass out of the body.
5. What is the half life of a radioactive
The average time it takes for the number of nuclei of the
material?
isotope in a sample to halve, or the time it takes for the
count rate from a sample to fall to half its initial level.
6. Francium 223 has a half life of 20 minutes.
0 minutes = 80 cpm
If the starting material 80 counts per minute,
20 minutes = 40 cpm
what would the counts per minute of
40 minutes = 20 cpm
Francium be after 1 hour?
1 hour = 10 cpm
7. Can you describe how to use a graph
You look at the 0 time point and find the counts per
showing the counts per minute and time a
minute (this is the maximum) then half this and use the
substance takes to decay to find the half life?
counts per minute axis to draw a line across to the half life
curve and, from this point, down to the time. This gives
you the half life.
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P2.6 Nuclear fission and nuclear fusion_1
Key Recall Question
1. Are nuclear power stations an example of
the use of nuclear fission or nuclear fusion?
2. What is nuclear fission?
3. Which two radioactive materials are
commonly used in nuclear reactors of power
stations?
4. What must the radioactive materials in a
nuclear reactor first do for fission to occur?
5. What happens when a nucleus in a reactor
undergoes nuclear fission?
6. What do the neutrons produced by nuclear
fission produce?
7. What is nuclear fusion?
8. Where is nuclear fusion most likely to be
observed?
9. How do stars form?
10. How do planets from?
Answer
Nuclear fission
The splitting of atomic nuclei.
Uranium-235 and plutonium-239
Absorb a neutron.
The nucleus splits into two smaller nuclei and two or three
neutrons. Energy is also released (which is the point in a
nuclear power station)
A chain reaction (the neutrons go on to be absorbed by
more uranium or plutonium nuclei).
The joining of two atomic nuclei.
In the stars.
When enough dust and gas from space is pulled together
by gravitational attraction.
When smaller masses are formed and are attracted by
larger masses due to the gravitational attraction.
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P2.6 Nuclear fission and nuclear fusion_2
Key Recall Question
Answer
1. What is special about a star during its ‘main
sequence’ and why does this happen?
2. What is the life cycle of a star determined
by?
3. A star is first formed from its protostar then
continues into the main sequence. After this it
can then go through two pathways depending
on the size. What is the pathway for stars
which are similar in size to the sun?
4. What is the pathway for stars which are
much bigger than the sun?
5. What else do the nuclear fusion processes
in the stars produce?
6. How are elements distributed across the
universe?
7. How are stars able to maintain their energy
output for millions of years?
It is stable because the forces within the star are balanced.
8. Which elements can be made in the main
sequence of a star?
9. Which elements are formed in supernovas?
Its size
(protostar main sequence)  red giant  white dwarf
 black dwarf
(protstar  main sequence)  red super giant 
supernova  neutron star or black hole
All of the naturally occurring elements
By an explosion of a massive star (supernova) at the end
of its life.
Hydrogen atoms are fused to form helium atoms which
releases energy. These fusion reactions can continue to
form bigger elements so this can carry on for millions of
years.
Elements up to iron.
Elements heavier then iron.
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