Free Marking Schemes For Form 2 Physics Exams

NAME……………………………………………………………..ADM/NO……………………

DATE…………………………. ………………… ………….CLASS……………………………

JOINT EXAMINATIONS

FORM 2

TERM THREE

PHYSICS 232

TIME: 2HRS

INSTRUCTIONS TO STUDENTS

Write your name and admission number in the spaces provided above.
The paper contains two sections, sections A and B
Answer all the questions in the spaces provided
All work must be clearly shown
Candidates should check the question paper to ascertain that all the 12 pages are printed as indicated and that no questions are missing.
Candidates should answer the questions in English

SECTION	QUESTION	MAXIMUM SCORE	CANDIDATE’SSCORE
A	1-12	25
B	13-18	55
TOTAL

SECTION A (25 MARKS)

Answer all questions in the spaces provided

The micrometre screw gauge below has a zero error of – 0.19mm.

Determine the actual thickness of the object. (2mks)

Two mirrored walls stand at an angle to each other. A student standing in the room counts nine images of himself in the mirrors. Determine the angle between the walls.

(3mks)

a) What is meant by the term anomalous expansion of water? (1mks)

………………………………………………………………………………………………………

b) Explain any two applications of contraction and expansion in solids. (2mks)

………………………………………………………………………………………………………

A body weighs 600N on the surface of the earth and 450N on the surface of another planet. Calculate the value of g in that planet (g on the earth = 10N/Kg) (3mks)

State two applications of electrostatic charges (2mks)

………………………………………………………………………………………………………

200 coulombs of charge pass through a point in a circuit for 0.6 minutes. What is the magnitude of the current flowing? (3mks)

While heating water in a beaker, a wire gauze is placed below the beaker explain.(2mks)

………………………………………………………………………………………………………

What is the relationship between physics and technology (2mks)

………………………………………………………………………………………………………

Using the domain theory distinguish between magnetic material and a magnet (2mks)

………………………………………………………………………………………………………

State two applications of convection in fluids (2mks)

………………………………………………………………………………………………………

Convert a temperature of 234K to degree celsius (1mk)

SECTION B (55 MARKS)

(a) State Hooke’s law (1mk)

………………………………………………………………………………………………………

(b) In an experiment to verify Hooke’s law, a piece of rubber was fixed to a rigid support and the other end was pulled with a force of ranging magnitude. The values of force and the extension were recorded in the table below:-

Force (N)	0	0.20	0.55	0.75	1.00	1.30	1.40
Extension(cm)	0	1.5	2.5	3.5	4.5	6.0	7.0

Plot a graph of force (Y-axis) against extension (X-axis) on the gird provided

(5mks)

From the graph, determine the spring constant of the rubber within the elastic limit (3mks)

What is the size of the force at the elastic limit (1mks)

(a) State three characteristics of a brake fluid. (1mk)

………………………………………………………………………………………………………

……………………………………………………………………………………………………

(b) The height of a mercury barometer at a particular place is 70cm. given that the density of mercury is 13600kgm³, determine;

(i) The atmospheric pressure at the place. (3mks)

(ii) The height of a water barometer at the same place. (Density of water=1g/cm³) (2mks)

(iii) Give a reason why mercury is preferred as a barometric liquid. (1mks)

(c) Calculate the minimum pressure a block of dimensions 3cm by 10cm by 15cm and mass 12kg could exert on a horizontal surface. (3mks)

a) Differentiate between transverse waves and longitudinal waves.(2mks)

………………………………………………………………………………………………………

The figure below shows a wave form in a string.

Given that the speed of the wave is 10m/s. With reference to this wave motion, determine;

(1mk)

(1mk)

(2mks)

Period (2mks)

A person standing 49.5m from the foot of a cliff claps his hands and hears an echo 0.3 seconds later. Calculate the velocity of the sound in the air. (3mks)

(a) What property of light is suggested by the formation of shadows? (1mk)

…………………………………………………………………………………………………

(b) A building standing 200m from a pinhole camera produces on the screen of the camera an image 2.5cm and height 5.0cm behind the pinhole.

Determine the actual height of the building (3mks)

(i) On the grid provided, draw to scale a ray diagram to locate the position of the image.(4mks)

(ii) State two applications of concave mirrors (2mks)

………………………………………………………………………………………………………

(a) When is an object said to be in stable equilibrium? (1mk)

………………………………………………………………………………………………………

(b) A uniform metal rod of length 80cm and mass 3.2kg is supported horizontally by two vertical springs balances C and D. Balance C is 20cm from one end while balance D is 30cm from the other end. Find the reading on each balance. (4mks)

(a) The figure below shows an electric bell. Briefly explain how it works. (4mks)

………………………………………………………………………………………………………

State the right-hand grip rule for straight conductor carrying current (1mks)

………………………………………………………………………………………………………

a) State the equation of continuity (1mk)

…………………………………………………………………………………………………….

b) The velocity of glycerin in a 5cm internal diameter pipe is 1.00m/s. Find the velocity in a 3cm internal diameter pipe that connects with it, both pipes flowing full. (3mks)

____________________________________________________________________

NAME……………………………………………………………..ADM/NO……………………

DATE…………………………. ………………… ………….CLASS……………………………

JOINT EXAMINATIONS

FORM 2

TERM THREE

PHYSICS 232

TIME: 2HRS

MARKING SCHEME

SECTION A (25 MARKS)

Answer all questions in the spaces provided

The micrometre screw gauge below has a zero error of – 0.19mm.

Determine the actual thickness of the object. (2mks)

The reading shown is 3.50

+ 0.01

3.51mm

Actual thickness = 3.51

+ 0.19

3.70mm

Two mirrored walls stand at an angle to each other. A student standing in the room counts nine images of himself in the mirrors. Determine the angle between the walls.

(3mks)

n =– 1 9=– 1

Ѳ=

=36⁰

a) What is meant by the term anomalous expansion of water? (1mks)

Anomalous expansion of water is defined as the unusual behaviour of water in which it contracts when heated and expands when cooled between 0 and 4⁰C

b) Explain any two applications of contraction and expansion in solids. (2mks)
Expansion joints in Steam Pipes

Pipes carrying steam are fitted with loops or expansion joints to allow for expansion when steam is passing through them and contraction when they are cooledFixing of Railway Line

Railway lines are constructed in sections with expansion gaps and the sections are held together by fishplates. The bolt holes in the rails are oval to allow free expansion and contraction of the rails as the bolts move freely in the holes.

A modern method of allowing for expansion and contraction in railways is to plane slant the rails so that they overlap

Installation of Telephone/ Electric Wires

They are loosely fixed to allow for contraction. Telephone or electric wires appear to be shorter and taut in the morning. When it is hot, the wires appear longer and slackened

Fixing of Steel Bridges

In bridges made of steel girders, one end is fixed and the other end is placed on rollers to allow for expansion and contraction.

A body weighs 600N on the surface of the earth and 450N on the surface of another planet. Calculate the value of g on that planet (g on the earth = 10N/Kg) (3mks)

Mass on the earth’s surface = 600

= 60Kg

Value of g in the other planet = 450

= 7.5N/Kg

State two applications of electrostatic charges (2mks)

Electrostatics precipitators
Fingerprinting
Spray painting

Photocopying

200 coulombs of charge pass through a point in a circuit for 0.6 minutes. What is the magnitude of the current flowing? (3mks)

Q=It

200=I×0.6×60

=5.556A

While heating water in a beaker, a wire gauze is placed below the beaker explain.(2mks)

The vessel is placed on a wire gauze because the gauze is a good conductor of heat it therefore spreads the heat to a large area of the vessel. Without gauze heat will concentrate at one point which may lead to uneven expansion of glass and hence break.

What is the relationship between physics and technology (2mks)

Machines used in the field of medicine such as X-rays, body scanners and lasers are all applications of physics.
The manufacture and use of satellites and microwave dishes used in information technology to relay information is based on physics knowledge
Physics knowledge is also used in the defence industry in the manufacture and use of most modern and complex machines.

Using the domain theory distinguish between magnetic material and a magnet (2mks)

For a magnet, the dipoles in all domains align towards a common direction while in magnetic magnetic material dipoles in every domain are aligned in different directions.

State two applications of convection in fluids (2mks)

Domestic hot water system
The cooling system of a car engine
Ventilation
Land and sea breeze

Convert a temperature of 234K to degree celsius (1mk)

T=Ѳ +273

234= Ѳ+273

Ѳ= 234-273= -39c

SECTION B (55 MARKS)

(a) State Hooke’s law (1mk)

For a helical spring or other elastic material, the extension is directly proportional to the stretching force, provided the elastic limit is not exceeded.

Force (N)	0	0.20	0.55	0.75	1.00	1.30	1.40
Extension(cm)	0	1.5	2.5	3.5	4.5	6.0	7.0

Plot a graph of force (Y-axis) against extension (X-axis) on the gird provided

(5mks)

Plotting=2mk

Scale=1mk

Line=1mk

Axes= 1mk

From the graph, determine the spring constant of the rubber within the elastic limit

(3mks)

K = F/E

Gradient = 0.75 – 0.2

3.5 – 1.0

= 0.5

2.5

= 0.2N/cm

What is the size of the force at the elastic limit (1mks)

1.3 N -check on the student graph where the straight line starts a bend

(a) State one characteristic of a brake fluid. (1mk)

-must be incompressible

-should not corrode the parts of the brake system

-have a high boiling point

-have a low freezing point

(b) The height of a mercury barometer at a particular place is 70cm. given that the density of mercury is 13600kgm³, determine;

(i) The atmospheric pressure at the place. (3mks)

Pa = 0.7×13600×10

=95200N/m²

(ii) The height of a water barometer at the same place. (Density of water=1g/cm³) (2mks)

95200=h×1000×10

h =

=9.52m

(iii) Give a reason why mercury is preferred as a barometric liquid. (1mks)

Mercury is much denser than water. It also supports a small and measurable column

(c) Calculate the minimum pressure a block of dimensions 3cm by 10cm by 15cm and mass 12kg could exert on a horizontal surface. (3mks)

Pmin=

=8000N/m²

a) Differentiate between transverse waves and longitudinal waves.(2mks)

In transverse waves, the vibration of the particles is at a right angle to the direction of wave travel while in longitudinal waves, the vibration of the particles is in a direction parallel to the direction of the wave travel.

b)The figure below shows a waveform in a string.

Given that the speed of the wave is 10m/s. With reference to this wave motion, determine;

(1mk)

50-10= 40m

(1mk)

(2mks)

f= velocity/wavelength

=10/40 = 0.25Hz

Period (2mks)

t= 1/f =1/0.25 = 4s

A person standing 49.5m from the foot of a cliff claps his hands and hears an echo 0.3 seconds later. Calculate the velocity of the sound in the air. (3mks)

(a) What property of light is suggested by the formation of shadows? (1mk)

Rectilinear propagation of light/light travels in a straight line

(b) A building standing 200m from a pinhole camera produces on the screen of the camera an image 2.5cm high and 5.0cm behind the pinhole.

Determine the actual height of the building (3mks)

hi = v

ho u

ho =2.5 x 20000

= 10000cm or 100m

(i) On the grid provided, draw to scale a ray diagram to locate the position of the image.(4mks)

ii) State two applications of concave mirrors (2mks)

-shaving mirrors

-By dentist to examine teeth

(a) When is an object said to be in stable equilibrium? (1mk)

A body is said to be in stable equilibrium if it returns to its original position after being displaced slightly.

(b) A uniform metal rod of length 80cm and mass 3.2kg is supported horizontally by two vertical spring balances C and D balance C is also from one end while balance D is 30cm from the other end. Find the reading on each balance (4mks)

When pivot at C:

Then C.M = (30 x 32) Ncm

A.C.M = 50D

C.M = A.C.M =>

D = 19.2N

C + D = 32N

C = 32 – 19.2

= 12.8N

Reading on C = 12.8N

Reading on D = 19.2N

(a) The figure below shows an electric bell. Briefly explain how it works. (4mks)

When the circuit is closed, the soft iron core gets magnetized and attracts the soft iron armature. The hammer being attached to the armature thus strikes the gong. the contacts break, the core loses magnetism and the armature returns to its normal position. The process repeats.

State the right-hand grip rule for straight conductor carrying current (1mks)

When a straight conductor is held with the right hand, with the thumb showing the direction of the current then the fingers show the direction of the magnetic field

a) State the equation of continuity (1mk)

AV= constant / A₁V₁=A₂V₂

a-area v- velocity

b) The velocity of glycerin in a 5cm internal diameter pipe is 1.00m/s. Find the velocity in a 3cm internal diameter pipe that connects with it, both pipes flowing full. (3mks)

A₁₌22/7*2.5*10^-4

A₂₌22/7* 1.5*10^-4

A₁V₁=A₂V₂

_V2=A₁V_1/A₂

22/7*2. 5²*10^{-4 *}1)/22/7* 1.5²*10^-4

=2.778M/S