Physics for BMAT
Understand the scope and level of
challenge of BMAT physics questions
Practice questions
Why physics?
Why physics?
Topics
1. Electricity
electrostatics, current, energy, power, transformers, electricity generation
2. Motion & energy
kinematics, forces, momentum, energy & conservation
3. Thermal physics & matter
conduction, convection, radiation, states of matter
4. Waves
nature of waves, erflection, refraction, Doppler effect, optics, sound
5. EM spectrum
nature of EM waves, properties, applications, dangers
6. Radioactivity
atomic structure, decay, ionising radiation, half-life, fission, fusion
Topic 1: Electricity
Four questions
1.1 – 1.4
Complete in four minutes
19 Which graph correctly shows how the resistance (R) varies with applied voltage (V) for a resistor
1.1
at constant temperature?
R
Resistors are ohmic,
they obey ohms law if
their temperature is
constant.
R
A
B
0
Ohm Law is that
V / I = constant (R)
0
0
0
V
R
V
i.e. R doesn’t change if
V changes
R
C
D
0
0
0
V
R
0
V
0
V
R
E
F
0
0
0
V
7
1.27
8
Which of the following is a correct unit of potential difference (voltage)?
A
amp per ohm
B
coulomb per joule
C
joule per second
D
newton per coulomb
✗
V=IxR
Volt = amps x ohms
✗
P=IxV &W=Pxt
so W = I x t x V
watt per amp
E
so V = W /(I x t)
amp = coulomb per second
I x t = coulomb per second x
second
= coulomb
A cube has unit length sides. What is the length of a line joining a vertex to the midpoint of one
volt = Joule per coulomb
of the opposite faces (the dashed line in the diagram below)?
✗
Newton is unit of force
✗
P=W/t
watt = joule per second
✔
P = I x V so V = P / I
Volt = watts per amp
A
2
1.3
P is in series – ammeter
Q is in parallel – voltmeter
R is in parallel – voltmeter
Closing the switch short circuits the righthand resistor, all of the current passes
through the closed switch (assume wires
have negligible resistance).
V = IR so p.d. measure by R decreases.
Battery’s terminal p.d. now mainly sits
across the left-hand resistor, so Q
increases
Effective resistance of circuit has fallen so
the current in the circuit measured at
point P increases
1.4
General formula: P = I x V
= I2 x R
= V2 / R
We need to know either the p.d. across resistor R1 or
the current passing through R1 to calculate power
dissipated.
Current is easier: emf, V = I x Rtotal
Rtotal = R1 + R2
So
I
= V/(R1+ R2)
Substitute for I:
P1 = I2 x R1 = V2 x R1 / (R1+ R2)2
Topic 2: Motion & energy
Four questions
2.1 – 2.4
Complete in four minutes
3
Shortly after opening her parachute, a free-fall parachutist of mass 60kg experiences the forces
shown in the diagram.
net force = 900N – 600N
= 300 N upwards
F=mxa
300 N = 60 kg x a
a = 300 / 60
= 5 m/s2
2.1
force is upwards so the
acceleration is upwards
weight = 600N
Which line in the table gives the size and direction of the acceleration of the parachutist at this
instance?
size of acceleration (m/s2)
direction of acceleration
A
5.0
downwards
B
10.0
downwards
C
5.0
upwards
D
10.0
upwards
E
0.0
-
22
2.2 27
A car of mass 800kg moves up an incline of 1 in 20 (1 in 20 means for every 20m along the road
the car gains 1m in height) at a constant speed of 20m/s. The frictional force opposing motion is
500N.
How much work has been done by the engine after the car has moved 50m?
A
20kJ
B
25kJ
C
27kJ
D
45kJ
E
65kJ
F
160kJ
Consider work done in 2.5 s:
50 m
2.5 m
ENDthrough
OF TEST a height of 2.5 m, so increasing its
1. Work is done to raise the car
GPE:
GPE = m x g x h = 800 kg x 10 N/kg x 2.5m = 20 000 J = 20 kJ
2. Work is done against friction:
W =Fxd
= 500 N x 50 m = 25 000 J
Work done = 45 kJ
= 25 kJ
2.3
A
F=mxa
100 N = 5kg x a
a = 100 / 5 = 20 m/s2
B
V=IxR
100 V = I x 5W
I = 100 / 5 = 20 A
C
Ek = ½ x m x v2
Ek = ½x0.4kgx100m2/s2
Ek = 20 J
D
v=fxl
0.2 m/s = 100 Hz x l
l = 0.2 / 100 = 0.002m
E
W =F x d
W = 0.2N x 100m
W = 20 J
23
In an ornamental fountain, water is squirted vertically upwards through a nozzle by a pump.
5kg of water pass through the nozzle each second, and the water reaches a height of 5m after
leaving the nozzle.
2.4
What is the power of the pump (assuming 100% efficiency), and at what speed does the water
leave the nozzle?
Conservation of energy
(Take g to be 10N/kg)
power of pump / W
speed of water / m/s
A
5
5
B
5
50
C
25
10
D
25
100
E
50
5
F
50
50
G
250
10
H
250
100
© UCLES 2010
KE at nozzle = GPE at top of fountain
Consider 5kg of water (pumped in 1 second)
GPE = m x g x h
= 5kg x 10 N/kg x 5m
= 250 J
KE = 250 J = ½ x 5 kg x v2
v2 = 500 / 5 = 100
v = 10 m/s
Each 5kg water has to have 250 J to reach the
observed height
So each second the pump output 250J
So power is 250 J/s, which is 250 W.
Topic 3: Thermal physics & matter
Four questions
3.1 – 3.4
Complete in four minutes
3.1
✗
✔
✔
3.2
Which of the following properties of a fluid moving through a pipe would need to
change in order to alter the flow rate of the fluid?
A.
B.
C.
D.
E.
Charge
Mass
Viscosity
Mass & viscosity
None of the above
Use logic:
Think of two fluids that have different flow rates,
e.g. water and custard.
Neither is charged so it is definitely not A
It is hard to know what mass means unless we are
given a specific volume, so it cannot be B or D.
Water has a low viscosity and flows quickly and
custard has a high viscosity and flows slowly, like
treacle, honey and other viscous substances.
The answer is C
3.3
Which of the following graphs shows the rate of heat transfer (with respect to
time) from boiling water in a saucepan to an egg dropped in having been
taken straight from the fridge?
B
The rate of heat transfer is proportional to the
temperature difference.
The temperature difference will be high at the start
and will fall as the egg heats up to eventually
become zero.
Time
Rate of transfer
D
Time
Rate of transfer
Time
C
Rate of transfer
Rate of transfer
A
Use logic:
Time
3.4
Liquids X, Y and Z have different densities, and do not mix.
A solid block is able to float in a bucket of liquid X.
The same block will fall to the bottom of a bucket of liquid Y
The volume of liquid Z is 0.5 times that of liquid X, by the mass of liquid Z is
0.6 times that of liquid X.
If a cylinder is filled with liquids X, Y and Z and left to separate, which of the
following describes the order of substances working from bottom to top?
A.
B.
C.
D.
E.
X, Y, Z
X, Z, Y
Y, X, Z
Y, Z, X
Z, X, Y
Most dense liquid will be at the bottom, least dense at the
top.
If the block float in X, then X is denser than the block
If the block sinks in Y, then Y is less dense than the block
So X is denser than Y.
If Z has 0.6 of the mass of X in 0.5 of the volume, r=m/V
r = (0.6 x m) / (0.5 x V) = 1.2 x m / V
i.e. Z is denser than X.
Z>X>Y
Topic 4: Waves
Four questions
4.1 – 4.4
Complete in four minutes
4.1 A runner is running along a road when the alarm system
of a stationary car she has just passed goes off. How fast is she
running if she hears the sound at 97.5% of the frequency
heard by someone standing still?
(Assume the speed of sound is 340 m/s)
Speed of sound, 340 m/s
Speed of runner, v
A.
B.
C.
D.
E.
She is not running
2.5 m/s
8.5 m/s
15 m/s
None of the above
Standing: 340 = f x l
Runner: 340 - v = 0.975f x l
l =
340/f = (340-v)/0.975f
340
340 x 0.975
v
= (340-v)/0.975
= 340 – v
= 340(1 – 0.975)
= 8.5 m/s
displacement (mm)
27 The first graph shows the variation of the displacement of particles with distance along a wave at a
particular instant in time:
4.2
18
60
0
distance (m)
2l
l
= 60 m
= 30 m
-18
displacement (mm)
The second graph shows the variation with time of the displacement of a particular particle in this
wave:
18
0.6
0
time (s)
-18
What is the speed of this wave?
A
30m/s
B
50m/s
C
90m/s
D
100m/s
E
150m/s
F
300m/s
3T
= 0.6 s
T
= 0.2s
f = 1/T = 1/0.2
= 5 Hz
v =fxl
= 5 Hz x 30 m
= 150 m/s
The depth of water in a particular tidal harbour varies with time as shown in the graph:
4.3
20
18
16
14
depth / metres
7
Tidal range = 6m
12
10
8
6
Period:
12 hours =
Period = 12 hours
4
2
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
time / hours
If the variation in depth caused by the effect of the tide is considered as a wave, what are the
amplitude and frequency of this wave?
amplitude / metres
frequency / hertz
A
3
1/(12 x 3600)
B
3
3600/12
C
6
1/(24 x 3600)
D
6
3600/24
E
8
1/(12 x 3600)
F
8
3600/12
G
16
1/(24 x 3600)
H
16
3600/24
12 hr
x 60 min/hr
x 60 s/min
= 12 x 3600 s
Frequency, f = 1 /T
= 1 / 12 x 3600
19
4.4
27 At the front of a long column of soldiers is a man regularly hitting a drum 50 times a minute. The
soldiers are told to place their left foot down on the ground when they hear the drum beat. The
column is so long that the soldiers at the back put down their left feet at the same time as the
soldiers in the front put down their right feet.
What is the minimum length of the column of soldiers?
[Speed of sound in air is 330m/s]
A
165m
B
198m
C
330m
D
396m
E
660m
F
792m
Left
Right
Left
Right
t = 0 min
t = 0.01 min
t = 0.02 min
t = 0.03 min
END OF TEST
Time taken for sound to reach the back of the
column is 0.01 minutes = 0.01 x 60 = 0.6 s
Distance covered, s
=vxt
= 330 m/s x 0.6 s
= 198 m
50 bpm
so period, T = 1/50 = 0.02min
Left
Right
Left
Right
t=0
t = 0.01 min
t = 0.02 min
t = 0.03 min
t = 0.04 min
Topic 5: EM spectrum
Four questions
5.1 – 5.4
Complete in four minutes
5.1
Bees see a higher frequency of electromagnetic
waves than humans. Consequently, which of the
following colours are bees more likely to be
attracted to?
Highest frequency corresponds to shortest wavelength
A. Red
Red has longest wavelength,
B. Yellow
violet has shortest wavelength.
So
C. Green
Red has lowest frequency
violet has highest frequency
D. Blue
E. Violet
15 The microwaves generated in a microwave oven travel through air at a speed of 3.0 x 108m/s,
with a wavelength of 12cm. They pass through plastic food containers, but at a reduced speed
of 2.0 x 108m/s.
5.2
What are the wavelength and frequency of these microwaves as they pass through a plastic
food container?
Wavelength (cm)
Frequency (Hz)
A
8
1.7 x 109
B
8
2.5 x 109
C
8
3.8 x 109
D
12
1.7 x 109
E
12
3.8 x 109
F
18
1.7 x 109
G
18
2.5 x 109
H
18
3.8 x 109
© UCLES 2012
In plastic, frequency doesn’t change, wavelength
shortens.
In air:
v
=fxl
3.0 x 108 m/s = f x 0.12 m
f
= 2.5 x 109 Hz
In plastic:
v
=fxl
2.0 x 108 m/s = 2.5 x 109 Hz x l
l = 0.08 m
= 8 cm
5.3
✔
✔
✗
17
23 A ray of orange light travelling through air has a speed of 3.0 x 108m/s and a wavelength of
600nm. (1nm = 10-9m)
What could be the speed, frequency and wavelength of this orange light when travelling through
glass?
Speed/ms-1
Frequency/Hz
Wavelength/nm
A
2.0 x 108
3.3 x 1014
400
B
2.0 x 108
3.3 x 1014
600
C
2.0 x 108
5.0 x 1014
400
D
2.0 x 108
5.0 x 1014
600
E
3.0 x 108
3.3 x 1014
400
F
3.0 x 108
3.3 x 1014
600
G
3.0 x 108
5.0 x 1014
400
H
3.0 x 108
5.0 x 1014
600
Speed of light through glass is SLOWER than through air/vacuum, so 2.0 x 108 m/s
Frequency of light doesn’t change in glass, but wavelength does.
Frequency of light in air v = f x l
8 /numbered
-91 to 6. One of=the
14but
24 I haveso
two six-sided
faces
from
dicexis10
fair,
f = v /dice,
l each
= 3with
x 10
600 x 10
5.0
Hzthe
other is not – it will land on numbers 1 to 5 with equal probability, but lands on 6 with a different
probability.
So
in glass, l = v / f = 2.0 x 108 / 5.0 x 1014 = 4.0 x 10-7 = 400.0 x 10-9 = 400 nm
When I roll the dice the probability that I get a total of 12 is
1
.
18
What is the probability that I get a total of 2 when I roll the dice?
5.4
Topic 6: Radioactivity
Four questions
6.1 – 6.4
Complete in four minutes
5
6.1
7
8
Which one of the following statements about nuclear physics is true?
✗
✗
✗
A
The process of emission of a gamma ray from a nucleus is called nuclear fission.
B
The half life of a radioactive substance is half the time taken for its nuclei to decay.
C
The number of neutrons in a nucleus is its atomic number (proton number) minus its
mass number.
D
The process used in nuclear power stations is nuclear fusion.
E
When a nucleus emits a beta particle, there is no change in the number of particles it
contains.
F
When a nucleus emits an alpha particle, one of its neutrons becomes a proton plus an
electron.
✗
✔
✗
If you look at a clock and the time is 9.45, what is the angle between the hour and the minute
hands?
A
0°
6.2
Source X:
24 hrs / 4.8 hrs = 5 half-lives
Count
Source Y:
= 320 x ½ x ½ x ½ x ½ x ½
= 320 x (1/2)5
= 10
24 hrs / 8 hrs = 3 half-lives
Count
= 480 x ( ½ )3
= 60
Total count = 10 + 60 = 70
It is known that a radioactive source emits a single type of radiation. Detectors are placed in
the two positions shown. The graph shows how the readings change over time.
30cm
source
detector 1
detector 2
1m
240
220
detector 1
200
count rate (counts/min)
11
6.3
Initial activity due to source = 200
180
160
140
120
100
Half initial activity due to
source = 100
80
60
40
detector 2
Background count = 20
20
0
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
time (hours)
Which type of radiation does the source emit, and what is its half-life?
type of radiation
half-life (hours)
A
alpha
2.40
B
alpha
2.76
C
beta
2.40
D
beta
2.76
E
gamma
2.40
F
gamma
2.76
Alpha particles would be absorbed
before reaching detector 1 at 30cm
Gamma rays would be detected at
detector 2 at 100 cm
Therefore beta radiation
3
In a laboratory experiment, protactinium-234 undergoes radioactive decay by β-emission into
uranium-234.
6.4
The table below describes how the mass of uranium-234 present in the sample varies with time
from the start of the experiment:
time / min
0.0
1.2
2.4
3.6
4.8
6.0
7.2
8.4
9.6
10.8
12.0
mass of u-234 / mg
0.0
8.0
12.0
14.0
15.0
15.5
15.7
15.9
15.9
16.0
16.0
16.0g
Using the information in the table, approximately what is the half-life of protactinium-234?
4
A
1.2 minutes
B
2.4 minutes
C
6.0 minutes
D
9.6 minutes
E
10.8 minutes
F
12.0 minutes
By the end of the time series the curve is flat
so almost all of the 234Pa has decayed into
234U. So there were originally 16g of 234Pa.
In one half-life the amount of 234Pa will have
halved, from 16g to 8g meaning the amount
of 234U will have risen from 0g to 8g.
i.e. after 1.2 minutes
I have two containers with different capacities. Initially, the larger one is full of water and the
smaller one is empty. I pour water from the larger container into the smaller container until they
Bonus questions
15 The graph represents the motion of a vehicle during part of a journey.
speed (m/s)
30
20
10
0
0
1
2
3
4
5
6
7
8
time (min)
What is the best estimate of the distance travelled during the part of the journey shown?
A
100.00m
B
107.50m
C
115.00m
D
6.00km
E
6.45km
F
6.90km
15 The graph represents the motion of a vehicle during part of a journey.
speed (m/s)
30
20
10
0
0
1
2
3
4
5
6
7
8
time (min)
What is the best estimate of the distance travelled during the part of the journey shown?
A
100.00m
B
107.50m
C
115.00m
D
6.00km
E
6.45km
F
6.90km
19 An object of mass 5kg falls from rest and hits the ground at a speed of 20m/s. Air resistance is
negligible.
From what height has the object fallen?
Take g to be 10m/s2
A
10m
B
20m
C
50m
D
100m
E
200m
F
1000m
19 An object of mass 5kg falls from rest and hits the ground at a speed of 20m/s. Air resistance is
negligible.
From what height has the object fallen?
Take g to be 10m/s2
A
10m
B
20m
C
50m
D
100m
E
200m
F
1000m
9
11 When radioactive isotopes decay, they sometimes have to go through a succession of
disintegrations to reach a stable isotope. These are called decay chains, and involve the
successive emission of numerous α and/or β particles.
One such isotope is radon-219 ( 219
86 Rn), which goes through a chain in which three α particles
and two β particles are emitted before reaching a stable isotope.
What are the atomic and mass numbers of the resulting stable isotope?
atomic number
mass number
A
80
207
B
80
211
C
82
207
D
82
215
E
85
211
F
85
219
G
86
215
H
86
219
9
11 When radioactive isotopes decay, they sometimes have to go through a succession of
disintegrations to reach a stable isotope. These are called decay chains, and involve the
successive emission of numerous α and/or β particles.
One such isotope is radon-219 ( 219
86 Rn), which goes through a chain in which three α particles
and two β particles are emitted before reaching a stable isotope.
What are the atomic and mass numbers of the resulting stable isotope?
atomic number
mass number
A
80
207
B
80
211
C
82
207
D
82
215
E
85
211
F
85
219
G
86
215
H
86
219
15 The circuit shows five identical filament bulbs designed to work at 12V connected in a circuit
with two switches. Switch P is initially open and switch Q is initially closed.
12V
switch P
bulb X
bulb Y
switch Q
Switch P is then closed and switch Q is opened.
Compared with their brightness before these changes were made, how has the brightness of
bulbs X and Y changed?
bulb X
bulb Y
A
brighter
brighter
B
brighter
dimmer
C
dimmer
brighter
D
dimmer
dimmer
E
unchanged
brighter
F
brighter
unchanged
15 The circuit shows five identical filament bulbs designed to work at 12V connected in a circuit
with two switches. Switch P is initially open and switch Q is initially closed.
12V
switch P
bulb X
bulb Y
switch Q
Switch P is then closed and switch Q is opened.
Compared with their brightness before these changes were made, how has the brightness of
bulbs X and Y changed?
bulb X
bulb Y
A
brighter
brighter
B
brighter
dimmer
C
dimmer
brighter
D
dimmer
dimmer
E
unchanged
brighter
F
brighter
unchanged
19 The diagrams below show velocity-time or distance-time graphs for 4 different objects, P, Q, R
and S.
velocity / m/s
velocity / m/s
12
10
8
6
4
2
0
4
8 12 16 20 24 28 32
0
1
2
P only
B
Q only
C
R only
D
S only
E
P and Q
F
Q and R
G
P and S
12
16
P
Q
3
4
5
20
24
175
150
125
100
75
50
25
0
6
0
60
120
180
time / s
time / s
R
S
Which graph(s) show an object accelerating at 2.4m/s2?
A
8
time / s
14
12
10
8
6
4
2
0
0
4
time / s
distance / m
distance / m
0
70
60
50
40
30
20
10
0
240
19 The diagrams below show velocity-time or distance-time graphs for 4 different objects, P, Q, R
and S.
velocity / m/s
velocity / m/s
12
10
8
6
4
2
0
4
8 12 16 20 24 28 32
0
1
2
P only
B
Q only
C
R only
D
S only
E
P and Q
F
Q and R
G
P and S
12
16
P
Q
3
4
5
20
24
175
150
125
100
75
50
25
0
6
0
60
120
180
time / s
time / s
R
S
Which graph(s) show an object accelerating at 2.4m/s2?
A
8
time / s
14
12
10
8
6
4
2
0
0
4
time / s
distance / m
distance / m
0
70
60
50
40
30
20
10
0
240