Perfect Score Physic f4-Answer
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ANSWER SCHEME
TOPIC : INTRODUCTION TO PHYSICS
SKILL 1 : KNOWLEDGE
What is meant by Statement
1. Physical quantity Physical characteristic that can be measured
2. Base quantities Quantities that cannot be defined in terms of other base quantities
3. Derived QuantitiesQuantities that obtained by combining base quantities by
multiplication, division or both these operations
4. Scalar quantities Quantities that have magnitude but no direction
5. Vector quantities Quantities that have both magnitude and direction
6. Accuracy How close the measurement made is to the actual value
5. Sensitivity Ability to detect a small change in the quantity to be measured
6. ConsistencyHow little deviation there is among the measurements made when a
quantity is measured several times
7. Zero error Error due to the pointer does not return to zero when not in use
SKILL 2 : UNDERSTANDING
Question 1
Accuracy is the ability of the instrument to give readings close to the actual value.
The value determined is accurate if it is near to the actual value
The consistency of a measuring instrument is the ability of instrument to record consistent readings for
each measurement with little deviation among readings.
The measurement is consistent if the values determined are close to each other.
Question 2
(a) To transfer heat faster from surroundings to the mercury
(b) mercury does not vaporize/ conducts heat well/ does not wet the sides of the tube/ thread
opaque
Question 3
(i) No
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SKILL 5 : PROBLEM SOLVING QUANTITATIVE
Question 1
(i) volume = 15cm x 20cm x 30 cm
= 9000 cm3
[2 marks]
= 9.0 x 103 cm3
(ii) volume = 9.0 x 103 cm3
= 9.0 x 10-3
m3. [2 marks]
(iii) Density = mass / volume
= 15 kg / 9.0 x 10-3 m3
= 1.67 x 103 kg m-3 [2 marks]
Question 2
(i) Thickness = 0.06 mm
= 0.06 x 10-3 m [1 mark]
(ii) Area = 20 cm x 10 cm
= 20 cm2
= 20 x 10-4 m2 [3marks]
SKILL 6 : DECISION MAKING
Question 1.
Characteristic Reason
Small range of measurement The estimate measurement is within a few mm only
Small division on scale Can give accurate reading
High sensitivity Can detect small change in measurement
No parallax error To obtain more accurate reading
Decision : M It has small range of measurement, small division
on scale, high sensitivity, and no parallax error
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Question 2
- The length of the rope is approximately same as the length needed
so that the length is not too long or too short.
- The density of the rope has to be smallto make it light
- The snapping force is larger
to ensure that the rope is not easily break.
- The diameter of the rope must smallerOccupy a smaller space
- The best choice is K because the length is approximately the same as
needed, low density, snapping force is bigger than the load and
Smaller diameter
2
2
2
2
2
TOPIC 2 : FORCE AND MOTION
SKILL 1 : KNOWLEDGE
TOPIC : Force and Motion
What is meant by Statement
1. Linear motion Motion along a straight line
2. Scalar quantity A physical quantity which has only magnitude
3. Vector quantity A physical quantity which has both magnitude and direction
4. Velocity The rate of change of displacement
5. Speed The rate of change of distance
6. Acceleration The rate of change of velocity
7. Distance The total length of the path travelled
8. Displacement Displacement is the shortest distance from one point to anotherpoint along a specific direction
9. Inertia The tendency of an object to resist change to its state of rest or
motion.
10.Newtons First law An object will remain at rest or motion with uniform velocityalong a straight line unless it is acted upon by an external
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What is meant by Statement
force.
11.Newtons Second law The net force on an object is proportional to the rate of changein momentum.
12.Newtons Third law To every action there is an equal and opposite reaction.13.Momentum The product of mass and velocity of an object
14.Principle ofconservation of
momentum
The total momentum of a system is constant if no external
forces act on the system.
15.Force A push or a pull that can change the size, shape or velocity ofan object.
16. Impulse Change of momentum.
17. Impulsive force A large force that acts for a short period of time during acollision or explosion
18.Weight The force of gravity which is exerted on it by earth.
19.Mass The amount of matter in the object.
20.Free fall Free fall occurs when an object falling under the force ofgravity only without being affected by any other external
forces.
.21.Work The product of force and the displacement along the direction
of the force
22.Energy The capacity to do work.
23.Gravitational field The region in which an object experiences a force due togravitational attraction.
24.Potential energy The Potential Energy of an object is the energy stored in theobject because of itsposition orstate.
25.Elastic potential energy The energy of an object when it is stretched or compressed
26.Kinetic energy The energy of an object due to its motion
27.The principle ofconservation of energy
Energy cannot be created or destroyed. It can be transformed
from one form to another, but the total energy in a closed
system is constant.
Power The rate at which work is done or energy is transferred.
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What is meant by Statement
28.Elasticity The property of an object that enables it to return to its originalshape and dimensions (size) after an applied external force is
removed.
29.Hookes law The extension of a spring is directly proportional to thestretching force provided the elastic limit is not exceeded.
30.Elastic limit The elastic limit of a spring is the maximum stretching forcewhich can be applied to the spring before it ceases to be
elastic.
31.Force constant (springconstant)
The force constant of a spring is the force per unit extension.
SKILL 2 : UNDERSTANDING
No Answers Mark
1
When the boy jumps onto the river bank, his momentum is forward. 1Using the Principle of conservation of momentum, 1
the total momentum before and after jumping is equal. 1
The boat moves backward to balance the forward momentum. 1
2
- Fuel burns in the combustion chamber
- Hot gases expelled at high speed backwards
- A large backwards momentum is produced
- In accordance to the principle of conservation of momentum, The rocket
gains forwards momentum of equal magnitude
1
1
1
1
3 - There are two types of force- Attraction and repulsive force between the particles of the solid.
- When the solid is stretched, the molecules displaced away from each other
- Attractive forces are acting to oppose the stretching
- When the solid is compressed, the molecules displaced closer to each other
- Repulsive forces are acting to oppose the compression
1
1
1
1
1
4 - The inertia of lorry and load is very big when it is moving
- The separate compartments make the load divided into smaller mass, thusreducing the ineatia of each unit.- The momentum of lorry and load is very big when it is moving and
produce abigger impulsive force.
- The steel structure will prevent the loads from smashing into the driverscompartment during emergency braking.
1
1
1
1
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SKILL 5 : PROBLEM SOLVING QUANTITATIVE
QUESTION ANSWER MARK
1
(i)Distance = 20 x 5
= 100 m2
(ii) 500 N 2
(iii)a = F / m = -500
800= -25 ms
-2
2
2
(a)The spring constant = gradient of the graphFor P , spring constant = 8 / 0.5 = 16 N cm
-1
For Q , spring constant = 3 / 0.5 = 6 Ncm-1
3
(b) Elastic potential energy = x 8 x 0.5 x 10-2
=0.02 J
2
3 (i)
Elastic potential energy 1
(ii) x
Fk ,
4
6.3k
k= 0.9 N cm-1
1
(iii)E = Fx
= x 3.6 x 4/100= 0.072 J
2
(iv) 9.0
5x
l = 12 5.56 = 6.44 cm
2
4
i
72 kmh-1 = 3600
100072x
= 20 ms-1
Impulse = mvmu= 0 (800 x 20)= 16000 Ns Ans + unit
1
1
1
ii.
Impulsive force = 2.0
16000
= 80000 N
11
5
(a)
(b)
(d)
(e)
500N
(i) 200 sin 300 N (ii) 200 cos 300 N
(i) 200 cos 300 = 173.2N
(ii) 173.2N = 50 aa = 3.464 m s-2
500 + 200sin 300
= 600 N
Because the total force acting perpendicular to the floor is smaller.
1
1 + 1
1
1
1
1
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QUESTION ANSWER MARK
6
(a)
(b)
(c)
(i) 400 N(ii) 40 N
In situation (i)
the longer the time of impact, the bigger the impulsive force.
1
1
1
1
SKILL 6 : DECISION MAKING
QUESTION
NO.ANSWER
MA
RK
1
(i)
Q is chosen because it has the highest spring constant, it is made of steel and has
the most number of coiled spring.
Characteristics Explanation
High spring constant Stiffer, more potential energy stored and
converted to kinetic energy. The kinetic energy
provided pushes the competitors higher up in
the air.
Steel frame Stronger, can support the competitor
More coiled springs Allows for higher bounces and morecomplicated stunts.
2
2
2
2
(ii)1. Jump harder/ push harder
2. To increase reactive force/ to store more energy
1
1
Total 10
2
Characteristic Reasons
Density of the material must be small To make the landing pad lighter /
easier to carry
Elasticity must be high Lengthen the time of impact to reduce
the impulsive force
Thickness must be thick Better absorb the impact // to reduce
the impulsive force
Air absorption must be high Release and absorb the air easily
- the most suitable material is R
Because its density is low, elasticity is high, it is thick and high absorption of air
1 + 1
1 + 1
1 + 1
1 + 1
1
1
3
suitability Reason
smalldiameter
enough space for the spring to beinstalled
High elastic
limit can support motorcylist up to 100kg
1
1
1
1
1
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higher spring
constant small compression of the spring
small natural
frequency
to reduce bumping
D , because has a small diameter , highest elastic limit ,highest spring constant and
small natural frequency
1
1
1
1
1
4 (a)
(b)
(c)
5N
(i) T1 = 4.16N(ii) T2 = 3.13 N
Picture in figure (a) because, the tension of the string is higher
1
22
2
Miscellaneous
1 F2 = 10 cos 30oN= 10 (0.866) N= 8.66 N
2
3 The trolleys move off separately in opposite directions.
F
x
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SKILL 6 : DECISION MAKING
1
Characteristics Reason
Streamlined shape To reduce water resistance
High strength of metal To withstand high water pressure
Wide base cross section
area
So that ship can float//prevent from
overturn // ship more stable // shipnot sink deeper
High volume of air spacein the ship
Produce air buoyant force// ship canfloat
Structure P Streamlined shape, High strength of
metal, Wide base cross section area,
High volume of air space in the ship
TOPIC : HEAT
SKILL 1 : KNOWLEDGE
What is meant by Statement
1. HeatHeat is a form of energy
2. Temperature Temperature is the degree.of hotness of a body
3. Thermal
equilibrium
Thermal equilibrium is reach when the net rate of heat transfer between the
two bodies is zero and its reach the same temperature.
4. Specific heat
Capacity , c
Specific heat capacity is defined as the amount of heat required to increase
the temperature of a mass of 1 kg by 1 C or 1 K.
c = Q , SI unit for c = J kg-1 C-1
m
5. Specific latent
Heat of fusion
Specific latent heat of fusion is defined as the quantity of heat energy
required to change 1 kg of a substance from the solid state to the liquid state,
without a change in temperature
Lf= Q , SI unit for L= J kg-1
m
6. Specific latent
heat of
vaporization
Specific latent heat of vaporization is defined as the quantity of heat energy
required to change 1 kg of a substance from the liquid state to the gaseous
state, without change in temperature
Lw= Q , SI unit for L= J kg-1
m
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7. Boyles LawBoyles Law states that for a fixed mass, at constant temperature, thepressure of gas is inversely proportional to its volume.
8.Charles LawCharles Law states that for a fixed mass at constant presure, the volume ofgas is directly proportional to its absolute temperature.
9. Pressure Law Pressure Law states that for a fixed mass at constant volume, the pressure ofgas is directly proportional to its absolute temperature. .
SKILL 2 : UNDERSTANDING
No Answers Mark
1
Thermometer is placed in the mouth of patient, 1
Heat is transferred from patients body to the thermometer 1
Thermal equilibrium between the thermometer and patients body is reached whenthe net rate of heat transfer is zero.
1
The thermometer reading shows the temperature of the patients body. 1
No Answers Mark
2
During the day,the land and the sea receive the same amount of heat from the sun.
1
Water has a higher specific capacity than the land 1
The land is heated to a higher temperature than the sea/The density of the air above
the sea is higher than the density of the air above the land.
1
The air above the land flows up and the air above the sea flows towards the land. 1
SKILL 3 : CONCEPTUALIZATION
QUESTION ANSWER MARK
1
(a)
1. Air molecules are in continuous random motion.
2. Air molecules collide with the wall of the glass tube and
bounces back.
3. This result in change in momentum and a force is exerted on the
wall.
4. Force per unit area is the pressure of the air.
4
(b) i Length of trapped air in condition Q is higher than in condition P. 1
ii Volume of trapped air in condition Q is higher than in condition P 1
iii Pressure in condition P is bigger than that in condition Q. 1
(c) i Length of trapped air is directly proportional to the volume of trapped air. 1
ii The volume of trapped air is inversely proportional with pressure 1
(d) Boyles law. 1
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QUESTION ANSWER MARK
2
(a)i The quantity of heat in water and cooking oil is equal 1
Ii The temperature of the water is lower than the temperature of the cooking oil 1
(b) i Specific heat capacity 1
iiThe higher the specific heat capacity of a material,the rate of increase of
temperature slower.
1
SKILL 4 : PROBLEM SOLVING QUALITATIVE
QUESTION
1
(i)
Lower fixed point
The thermometer is placed in pure melting ice
When the mercury level is steady, its position in glass stem of
the thermometer is marked as 0oC .
Upper fixed point
The thermometer is placed in a container that is surrounded by steam of boilingwater at ordinary atmospheric pressureWhen the mercury level is steady, its position on the glass stem of the thermometer
is marked as 100oC .
The distance on the stem of the thermometer between 0oC and 100
oC is measured,
then divided equally into 100 parts. (Each part represents 1oC)
1
1
1
1
1
1
(ii)
L - Lo x 100oC
L100 - Lo
= 10.0 - 2.5 x 100 oC
13.82.5
= 66.37oC
1
1
1
2
(i)Heat is absorbed by the metal block
1
(ii)
The rate of heat flows between metal block and the water is the same.
The water and the metal block achieve thermal equilibrium.
1
1
(iii)
mwater x cwater x water = mmetal blockx cmetal blockx metal blockcmetal block= 0.1 x 4200 x (48-28)
0.5 x (48-28)
= 840 J kg-1
C-1
1
1
QUESTION
NO.
ANSWERMA
RK
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3
(i)
Modifications Reason
thermometer is made from
transparent glass that is strong
so that it is not easily broken
the thermometric liquid chosen ismercury
because it easily expandsuniformly
the capillary tube is made narrowand thin
so that it is more sensitive
the shape of the thermometer is
round
so that it has a magnifying effect
the thermometer is placed in
melting ice to obtain the lower
point
the thermometer is placed in
steam from boiling water to
obtain the upper point
2
2
2
2
2
Total 10
SKILL 5 : PROBLEM SOLVINGQUANTITATIVE
QUESTIO
NANSWER
MAR
K
1
(i)P = Patm + Pwater
= 10 + 0.5
= 10.5 m water
1
(ii)
P1V1 = P2V2V
1=
P
2V
2P1= 10.5 x 0.5
10
= 0.525 cm3
1
1
2
(a)
L =m
Pt
= 0.1 x 103
x 156
0.05
= 312000 J kg-1
1
1
(b)
t = 72 s (from graph)
c = Pt
m = 0.1 x 10 3 x 72
0.05 x 140
= 1028.57 J kg-1
C
1
1
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QUESTIO
NANSWER
MAR
K
1
SKILL 6 : DECISION MAKING
QUESTIO
N
NO.
ANSWERMA
RK
1
(i)
K is the most suitable liquid
Because of its low freezing point, high boiling point, high specific of heat capacity
and low ability to react with metals
Characteristics Explanation
High boiling point It will not boil easily when absorbing heat
from the engine
Low freezing point It will not freeze during cold weather//can flow
at low temperature
High specific heat
capacity
It can transfer a big quantity of heat with small
rise in temperature
A low ability to react
with metals
The metal parts of the engine will not corrode
easily
2
2
2
2
1
1
Total 10
QUESTIO
N
NO.
ANSWERMA
RK
2 (i) R ischosen
because
Low
specific heat capacity of ice cream box, Smaller size of ice cream box, Plastic PVC,
Bright color of outer box
Characteristics Explanation
Low specific heat capacity
of ice cream box
Easy get cold // becomes cool quickly
Smaller size of ice cream
box
Easier to carry // easy too become cool
Plastic PVC Poor conductor of heatBright colour of outer box Does not absorb heat from surrounding
quickly
2
2
2
2
1
1
Total 10
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Miscellaneous
1 Rate of change of momentum of the molecules increases
2
3 Aluminium contains more heat energy than Copper
p
1