Perfect Score Physic f4-Answer

7/31/2019 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


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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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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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.


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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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


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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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


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. .


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


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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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


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


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


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

Perfect Score Physic f4-Answer

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