Download Grade 11 IB DP Physics Mock Exam – Chapters 1.1 – 4.1

Grade 11 IB DP Physics Mock Exam – Chapters 1.1 – 4.1
Questions
1.
This question is about the photoelectric effect.
Light is incident on a clean metal surface in a vacuum. The maximum kinetic energy KEmax of
the electrons ejected from the surface is measured for different values of the frequency f of the
incident light.
The measurements are shown plotted below.
2.0
1.5
KEmax / × 10–19 J 1.0
0.5
0.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
14
f / × 10 Hz
(a)
Draw a line of best fit for the plotted data points.
(1)
(b)
Use the graph to determine
(i)
the Planck constant;
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(2)
(ii)
the minimum energy required to eject an electron from the surface of the metal (the
work function).
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(3)
1
(c)
Explain briefly how Einstein’s photoelectric theory accounts for the fact that no electrons
are emitted from the surface of this metal if the frequency of the incident light is less than
a certain value.
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(3)
(Total 9 marks)
2.
When a body is accelerating, the resultant force acting on it is equal to its
A.
change of momentum.
B.
rate of change of momentum.
C.
acceleration per unit of mass.
D.
rate of change of kinetic energy.
(1)
3.
A sphere of mass m strikes a vertical wall and bounces off it, as shown below.
wall
momentum pB
momentum pA
2
The magnitude of the momentum of the sphere just before impact is pB and just after impact is
pA. The sphere is in contact with the wall for time t. The magnitude of the average force exerted
by the wall on the sphere is
A.
 pB – p A 
B.
 pB  p A 
C.
 pB – p A 
D.
 pB  p A 
t
t
mt
mt
.
.
.
.
(1)
4.
This question is about an experiment designed to investigate Newton’s second law.
In order to investigate Newton’s second law, David arranged for a heavy trolley to be
accelerated by small weights, as shown below. The acceleration of the trolley was recorded
electronically. David recorded the acceleration for different weights up to a maximum of 3.0 N.
He plotted a graph of his results.
heavy trolley
acceleration
pulley
weight
3
(a)
Describe the graph that would be expected if two quantities are proportional to one
another.
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(2)
(b)
David’s data are shown below, with uncertainty limits included for the value of the
weights. Draw the best-fit line for these data.
1.40
acceleration
/ ms–2
1.20
1.00
0.80
0.60
0.40
0.20
0.00
0.00
0.50
1.00
1.50
2.00
2.50
weight / N
(2)
4
(c)
Use the graph to
(i)
explain what is meant by a systematic error.
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(2)
(ii)
estimate the value of the frictional force that is acting on the trolley.
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(1)
(iii)
estimate the mass of the trolley.
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(2)
(Total 9 marks)
5.
An object is moving at constant velocity. Which one of the following quantities must have zero
magnitude?
A.
Weight of object
B.
Momentum of object
C.
Kinetic energy of object
D.
Resultant force on object
(1)
5
6.
An elevator (lift) is used to either raise or lower sacks of potatoes. In the diagram, a sack of
potatoes of mass 10 kg is resting on a scale that is resting on the floor of an accelerating
elevator. The scale reads 12 kg.
elevator
10 kg
scale
The best estimate for the acceleration of the elevator is
A.
2.0 m s–2 downwards.
B.
2.0 m s–2 upwards.
C.
1.2 m s–2 downwards.
D.
1.2 m s–2 upwards.
(1)
7.
A light inextensible string has a mass attached to each end and passes over a frictionless pulley
as shown.
pulley
string
mass M
mass m
6
The masses are of magnitudes M and m, where m < M. The acceleration of free fall is g. The
downward acceleration of the mass M is
A.
B.
M  m g .
M  m 
M  mg .
M
C.
M  m g .
M  m 
D.
M  m 
Mg
.
(1)
7
8.
This question is about a balloon used to carry scientific equipment.
The diagram below represents a balloon just before take-off. The balloon’s basket is attached to
the ground by two fixing ropes.
balloon
basket
fixing rope
50
fixing rope
50
ground
There is a force F vertically upwards of 2.15  103 N on the balloon. The total mass of the
balloon and its basket is 1.95  102 kg.
(a)
State the magnitude of the resultant force on the balloon when it is attached to the ground.
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(1)
(b)
Calculate the tension in either of the fixing ropes.
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(3)
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(c)
The fixing ropes are released and the balloon accelerates upwards. Calculate the
magnitude of this initial acceleration.
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(2)
(d)
The balloon reaches a terminal speed 10 seconds after take-off. The upward force F
remains constant. Describe how the magnitude of air friction on the balloon varies during
the first 10 seconds of its flight.
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(2)
(Total 8 marks)
9.
Thermal energy is transferred through the glass windows of a house mainly by
A.
conduction.
B.
radiation.
C.
conduction and convection.
D.
radiation and convection.
(1)
9
10.
A
thermometer
V
heater
metal block
The specific heat capacity of a metal block of mass m is determined by placing a heating coil in
its centre, as shown in the diagram above.
The block is heated for time t and the maximum temperature change recorded is Δθ. The
ammeter and voltmeter readings during the heating are I and V respectively.
Which one of the following is not a source of error in the experiment?
A.
Some thermal energy is retained in the heater.
B.
The thermometer records the temperature at one point in the block.
C.
Some thermal energy is lost from the variable resistor in the circuit.
D.
The block is heated at its centre, rather than throughout its whole volume.
(1)
10
11.
A
thermometer
V
heater
metal block
The specific heat capacity of a metal block of mass m is determined by placing a heating coil in
its centre, as shown in the diagram above.
The block is heated for time t and the maximum temperature change recorded is Δθ. The
ammeter and voltmeter readings during the heating are I and V respectively.
The specific heat capacity is best calculated using which one of the following expressions?
VIt
m
A.
c=
B.
c=
C.
c=
m
VI
D.
c=
m
VIt
VI
m
(1)
11
12.
This question is about the change of phase (state) of ice.
A quantity of crushed ice is removed from a freezer and placed in a calorimeter. Thermal energy
is supplied to the ice at a constant rate. To ensure that all the ice is at the same temperature, it is
continually stirred. The temperature of the contents of the calorimeter is recorded every 15
seconds.
The graph below shows the variation with time t of the temperature θ of the contents of the
calorimeter. (Uncertainties in the measured quantities are not shown.)
20
15
10
5
C
0
–5
–10
–15
–20
0
25
50
75
100
125
150
175
200
t/s
(a)
On the graph above, mark with an X, the data point on the graph at which all the ice has
just melted.
(1)
(b)
Explain, with reference to the energy of the molecules, the constant temperature region of
the graph.
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(3)
12
The mass of the ice is 0.25 kg and the specific heat capacity of water is 4200 J kg–1 K–1.
(c)
Use these data and data from the graph to
(i)
deduce that energy is supplied to the ice at the rate of about 530 W.
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(3)
(ii)
determine the specific heat capacity of ice.
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(3)
(iii)
determine the specific latent heat of fusion of ice.
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(2)
(Total 12 marks)
13
13.
This question is about thermal physics.
(a)
Explain why, when a liquid evaporates, the liquid cools unless thermal energy is supplied
to it.
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(3)
(b)
State two factors that cause an increase in the rate of evaporation of a liquid.
1. .................................................................................................................................
2. .................................................................................................................................
(2)
(c)
Some data for ice and for water are given below.
Specific heat capacity of ice
Specific heat capacity of water
Specific latent heat of fusion of ice
= 2.1 × 103 J kg–1 K–1
= 4.2 × 103 J kg–1 K–1
= 3.3 × 105 J kg–1
A mass of 350 g of water at a temperature of 25°C is placed in a refrigerator that extracts
thermal energy from the water at a rate of 86 W.
Calculate the time taken for the water to become ice at –5.0°C.
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(4)
(Total 9 marks)
14
14.
This question is about specific heat capacity and a domestic shower.
(a)
Define the term specific heat capacity.
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...................................................................................................................................
(1)
(b)
Equal masses of two different solid substances A and B are at the same temperature. The
specific heat capacity of substance A is greater than the specific heat capacity of
substance B. The two substances now have their temperatures raised by the same amount.
Explain which substance will have the greater increase in internal energy assuming both
remain in the solid phase.
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(2)
(c)
In an experiment to measure the specific heat capacity of a metal, a piece of the metal is
immersed in boiling water and left there for several minutes. It is then transferred quickly
into some cold water in a calorimeter. The water is stirred and the maximum temperature
of the water is recorded.
(i)
State why the metal is left in the boiling water for several minutes.
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(1)
15
(ii)
Write down a word equation for the thermal energy QM lost by the metal to the
water.
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(1)
(iii)
Write down a word equation for the thermal energy QW gained by the water in the
calorimeter.
.........................................................................................................................
.........................................................................................................................
(1)
(iv)
A value of the specific heat capacity of the metal may be calculated from (ii) and
(iii) by assuming that QM = QW.
State why in practice, this assumption leads to an error in the calculated value of
the specific heat capacity.
.........................................................................................................................
.........................................................................................................................
(1)
(d)
The diagram below shows part of the heating circuit of a domestic shower.
insulated wire
water pipe
240V
supply
hot water 40C
cold water 14C
insulated heating element
Cold water enters the shower unit and flows over an insulated heating element. The
heating element is rated at 7.2 kW, 240 V. The water enters at a temperature of 14C and
leaves at a temperature of 40C. The specific heat capacity of water is 4.2  103 J kg−1
K−1.
16
(i)
Describe how thermal energy is transferred from the heating element to the water.
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(3)
17
(ii)
Estimate the flow rate in kg s−1 of the water.
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(4)
(iii)
Suggest two reasons why your answer to (b) is only an estimate.
1.
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2.
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(2)
(iv)
Calculate the current in the heating element when the element is operating at 7.2
kW.
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(2)
(v)
Explain why, when the shower unit is switched on, the initial current in the heating
element is greater than the current calculated in (iv).
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(2)
18
(e)
In some countries, shower units are operated from a 110 V supply. A heating element
operating with a 240 V supply has resistance R240 and an element operating from a 110 V
supply has resistance R110.
(i)
Deduce, that for heating elements to have identical power outputs
R110
 0.21.
R240
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(3)
19
(ii)
Using the ratio in (i), describe and explain one disadvantage of using a 110 V
supply for domestic purposes.
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(2)
(Total 25 marks)
15.
This question is about modelling the thermal processes involved when a person is running.
When running, a person generates thermal energy but maintains approximately constant
temperature.
(a)
Explain what thermal energy and temperature mean. Distinguish between the two
concepts.
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(4)
20
The following simple model may be used to estimate the rise in temperature of a runner
assuming no thermal energy is lost.
A closed container holds 70 kg of water, representing the mass of the runner. The water is
heated at a rate of 1200 W for 30 minutes. This represents the energy generation in the runner.
(b)
(i)
Show that the thermal energy generated by the heater is 2.2 × 106 J.
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(2)
(ii)
Calculate the temperature rise of the water, assuming no energy losses from the
water. The specific heat capacity of water is 4200 J kg−1 K−1.
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(3)
(c)
The temperature rise calculated in (b) would be dangerous for the runner. Outline three
mechanisms, other than evaporation, by which the container in the model would transfer
energy to its surroundings.
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(6)
21
A further process by which energy is lost from the runner is the evaporation of sweat.
(d)
(i)
Describe, in terms of molecular behaviour, why evaporation causes cooling.
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(3)
(ii)
Percentage of generated energy lost by sweating: 50%
Specific latent heat of vaporization of sweat: 2.26 × 106 J kg−1
Using the information above, and your answer to (b) (i), estimate the mass of sweat
evaporated from the runner.
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(3)
(iii)
State and explain two factors that affect the rate of evaporation of sweat from the
skin of the runner.
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(4)
(Total 25 marks)
16.
This question is about projectile motion and the use of an energy argument to find the speed
with which a thrown stone lands in the sea.
22
Christina stands close to the edge of a vertical cliff and throws a stone. The diagram below (not
drawn to scale) shows part of the trajectory of the stone. Air resistance is negligible.
P
15 m s –1
O
Q
25 m
sea
Point P on the diagram is the highest point reached by the stone and point Q is at the same
height above sea level as point O.
(a)
At point P on the diagram above draw arrows to represent
(i)
the acceleration of the stone (label this A).
(1)
(ii)
the velocity of the stone (label this V).
(1)
The stone leaves Christina’s hand (point O) at a speed of 15 m s−1 in the direction shown. Her
hand is at a height of 25 m above sea level. The mass of the stone is 160 g. The acceleration due
to gravity g = 10 m s−2.
(b)
(i)
Calculate the kinetic energy of the stone immediately after it leaves Christina’s
hand.
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23
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(1)
(ii)
State the value of the kinetic energy at point Q.
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(1)
(iii)
Calculate the loss in potential energy of the stone in falling from point Q to hitting
the sea.
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(1)
(iv)
Determine the speed with which the stone hits the sea.
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(2)
(Total 7 marks)
17.
A machine lifts an object of weight 1.5 × 103 N to a height of 10 m. The machine has an overall
efficiency of 20%. The work done by the machine in raising the object is
A.
3.0 × 103 J.
B.
1.2 × 104 J.
C.
1.8 × 104 J.
D.
7.5 × 104 J.
(1)
18.
This question is about power.
(a)
Define power.
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24
.....................................................................................................................................
(1)
(b)
A constant force of magnitude F moves an object at constant speed v in the direction of
the force. Deduce that the power P required to maintain constant speed is given by the
expression
P = Fv
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(2)
(c)
Sand falls vertically on to a horizontal conveyor belt at a rate of 60 kg s–1.
sand
60 kg s-1
2.0 m s-1
The conveyor belt that is driven by an engine, moves with speed 2.0 m s–1.
When the sand hits the conveyor belt, its horizontal speed is zero.
(i)
Identify the force F that accelerates the sand to the speed of the conveyor belt.
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(1)
25
(ii)
Determine the magnitude of the force F.
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(2)
(iii)
Calculate the power P required to move the conveyor belt at constant speed.
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(1)
(iv)
Determine the rate of change of kinetic energy K of the sand.
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(2)
(v)
Explain why P and K are not equal.
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(2)
26
(d)
The engine that drives the conveyor belt has an efficiency of 40%. Calculate the input
power to the engine.
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(2)
(Total 13 marks)
19.
Mechanical power
(a)
Define power.
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(1)
(b)
A car is travelling with constant speed v along a horizontal straight road. There is a total
resistive force F acting on the car.
Deduce that the power P to overcome the force F is P = Fv.
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(2)
27
(c)
A car drives up a straight incline that is 4.8 km long. The total height of the incline is 0.30
km.
The car moves up the incline at a steady speed of 16 m s–1. During the climb, the average
friction force acting on the car is 5.0  102 N. The total weight of the car and the driver is
1.2  104 N.
(i)
Determine the time it takes the car to travel from the bottom to the top of the
incline.
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(2)
(ii)
Determine the work done against the gravitational force in travelling from the
bottom to the top of the incline.
.........................................................................................................................
(1)
(iii)
Using your answers to (c)(i) and (c)(ii), calculate a value for the minimum power
output of the car engine needed to move the car from the bottom to the top of the
incline.
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(4)
28
(d)
From the top of the incline, the road continues downwards in a straight line. At the point
where the road starts to go downwards, the driver of the car in (c), stops the car to look at
the view. In continuing his journey, the driver decides to save fuel. He switches off the
engine and allows the car to move freely down the hill. The car descends a height of 0.30
km in a distance of 6.4 km before levelling out.
The average resistive force acting on the car is 5.0  102 N.
Estimate
(i)
the acceleration of the car down the incline.
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(5)
(ii)
the speed of the car at the bottom of the incline.
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(2)
(e)
In fact, for the last few hundred metres of its journey down the hill, the car travels at
constant speed. State the value of the frictional force acting on the car whilst it is moving
at constant speed.
...................................................................................................................................
(1)
(Total 18 marks)
29