# Physics Solved Past Paper 10th Class 2013 Karachi Board

SECTION ‘A’ MULTIPLE CHOICE QUESTION

1. Choose the correct answer for each from the given options.

(i)The book ‘Kitab-ul-Manazir’ is written by:
(a)Ibn-al-Haitham
(b) Al-Beruni
(c)Yakoob Kindi

(ii)1 pico second = ——– second.
(a)10-³
(b) 10-6
(c) 10-9
(d) 10-¹²

(iii)The rate of change of velocity is known as:
(a)Displacement
(b) Acceleration
(c)Uniform motion
(d) speed

(iv) Newton’s First Law of Motion gives the concept of:
(a)Energy
(b) intertia
(c) Momentum
(d) force

(v)Negative of a vector is that vector which is equal in magnitude, but:
(a) Same in direction
(b) Opposite in direction
(c)Perpendicular
(d) None of them

(vi)If the centre of gravity of a body is lower than its point of support, then its equilibrium will be:
(a)Static
(b) Unstable
(c) Neutral
(d) Stable

(vii)The mass of the earth is:
(a)6 x 1024 slugs
(b) 6 x 1024 g
(c) 6 X 1024 N
(d) 6 x 1024 kg

(viii)The S.l. Unit of energy is:
(a)newton
(b) joule
(c) kilogram
(d) coulomb

(ix)It is a second kind of lever:
(a)Human arm
(b) Door
(c) Scissors
(d) See-saw

(x)Archimedes’ Principle is applied to determine:
(a)Specific heat
(b) Specific gravity
(c)Specific resistance
(d) Latent heat

(xi)The conversion of liquids into vapours at all temperatures is called:
(a)Boiling
(b) Melting
(c) Evaporation
(d) Sublimation

(xii)Sound waves are:
(a)Transverse waves
(c) Longitudinal waves
(d) Electromagnetic wave

(xiii)For total internal reflection the angle of incidence must be ——– the critical angle:
(a) Greater than
(b) Less than
(c) Equal to
(d) Half of

(xiv)A ray of white light thrown onto a glass-prism cannot be
(a) Deviated
(b) Dispersed
(c) Focused
(d) Refracted

(xv)Three resistances of 3 n are connected in parallel. Their total resistance will be:
(a) 3Ω
(b) 9 Ω
(c)
(d) 1/3Ω

(xvi) To measure potential difference the voltmeter is always connected in the circuit in:
(a) series
(b) parallel
(c) any way
(d) parallel to Ammeter

(xvii) The elements having atomic number greater than 82 are called:
(a) Semiconductors
(b) Conductors
(d) Insulators

2. Define Physics and write the names of its any four branches

DEFINITION OF PHYSICS:

Physics is the branch of science which offers the study of properties of matter and energy along with the interaction between them.

FOUR IMPORTANT BRANCHES OF PHYSICS ARE:

(i) Machanics
(ii) Electricity
(iii) Plasma Physic
(iv) Atomic Physics

3. Write 5.1. units of the following physical quantities:

(i) length
(ii) – electric current
(iv) work
(iii)pressure
(iv) work
(v) volume
(vi)force

4. The velocity of a car increases by an acceleration of 2 m/s² and becomes 20 m/s in 5 seconds. Find the initial velocity of the car.

5. Write three differences between Mass and Weight.

MASS

1. The quantity of matter present in a body is called mass. It is also a measure of the inertia of body
2. Mass remains constant  whether on earth or away  from it.
3. Mass has no direction.

WEIGHT

1. The force with which a body is attracted towards the earth is called Weight
2. Weight is not constant and decreases with height.
3. Weight acts towards the centre of the earth

Define Torque. Write down its unit and formula.

TORQUE: Torque is defined as the turning effect of a force about a point of rotation.

FORMULA:
Torque = Force x moment arm
t = F x d
Where symbol t is used for torque.
5.1.UNIT: The unit of torque in S.1.system is Newton metre.

NEWTON’S LAW OF GRAVITATION

Newton’s law of gravitation states that every body in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to square of the distance between them

Consider two spherical bodies A and B of masses “m-” and “m2” respectively placed such that the distance between their centers is “d”.

The force of attraction F between them according to the law of universal gravitation is:

Where G is the constant of proportionally known as Gravitational constant.
In S.1.Unit value of Gis 6.67 X 10-¹ N – m²/ Kg

8. Define Work and Energy. State the Law of Conservation of Energy.

WORK: When a force acts on a body and moves it through some distance, work is said to be done.
ENERGY: The capability of doing work is called energy. LAW OF CONSERVATION OF ENERGY

State that energy can neither be created nor destroyed, but it changes from one form to another. The total energy remains constant.

9. Find the two rectangular components of a force of 100N which is acting at an angle of 60° with X-axis (sin 60° = 0.866, cos 60°-= 0.5)

Data: F=100N 9=60° Fx=? Fy=?

SOLUTION: 10. Define the following:

(i) Lever
(ii) Inclined Plane
(iii) Pully

(i) Lever

It is a simple machine which consists of a rigid bar capable of turning about a fixed point, called “Fulcrum”. Effort is applied at one end and weight can be lifted at the other end.

(ii) Inclined Plane

It is a simple plane surface making an angle e (acute.angle) with the horizontal surface. It helps in raising heavy loads.

(iii) Pully

A pulley is a grooved wheel, supported in a frame called block. A rope passes over the pulley and when the rope is pulled the pulley rotates.

Pulley can be (i) Fixed pulley and (ii) Movable pulley

11. State the following laws I principles

(i) Hooke’sLaw
(ii) Pascal’sLaw
(iii) Archimedes’ Principle

(i) HOOK’S LAW:

It states that within elastic limit, stress is directly proportional to strain.

(ii) PASCAL’S LAW:

When pressure is applied to a liquid in a vessel it is transmitted undiminished equally in all directions and acts perpendicularly to the walls of the container.

(iii) Archimedes’ Principle

When an object is immersed in a liquid, an up trust acts upon it which is equal to’ the weight of the liquid displaced by the object

12. Calculate the length of a Second’s Pendulum(g=10ms²)

A second pendulum is that whose time period is 2 seconds

Data: t = 2 sec. g = 9.8 m/s² L = ?

13. Write three characteristics formed in a plane mirror.

CHARACTERISTICS OF IMAGE FORMED BY PLANE MIRROR:

(i) The image is virtual Le.cannot be taken on a screen.
(ii) The ln. ‘ge is as for behind the mirror as the object is in front of it.
(iii) The image is laterally inverted, i.e. the right-side of the object appears as the left side of the image.
(iv) The image is of the same size as the object

14. Find the focal length of a convex lens if p = 5cm, q = 10cm & the image formed is virtual.

15. Define ‘Reflection of Light’. State the two Laws of Reflection of Light.

DEFINITION

When light traveling through some medium strikes the surface of another medium, a part of it is thrown back in the same medium. This is called Reflection of light

LAWS OF REFLECTION:

(1) The angle of incidence is equal to the angle of reflection.
L i = L r
(2) The incident ray, the reflected ray and the normal all lie in the same plane

16. Define the following:

(i) Dispersion of light
(ii) Photon
(iii) Rainbow

(i) DISPERSION OF LIGHT:

The splitting up of white light into its constituent colours is called Dispersion of light.

(ii) PHOTON:

Photon is the name for packets of energy given out by a hot body, according to Quantum Theory of light.

(iii) RAINBOW:

Rainbow is an arc of spectral colours formed across the sky after rainfall in morning or evening. When sun rays fall obliquely on rain drops, they behave like prisms and disperse white light into seven clours

17. State the following laws:

(i) Coulomb’s Law
(ii) Ohm’s Law
(iii) Joule’s Law

(i) COULOMB’S LAW:

It states that the magnitude of
electrostatic force between two point charges is directly
proportional to the product of magnitude of charge & inversely
propositional to the square of the dista’1Fe between them

(ii) OHM’S LAW:

It states that the current passing through a conductor is directly proportional to the potential difference applied across the ends provided the temperature and other physical condition of the conductor is kept constent

(iii) JOULE’S LAW

When electric current passes through a conductor, the energy produced is proportional to the work done by the current.

Mathematically W = Ι² Rt.

18. Three resistances of 4 Ω, 6 Ω and 12 Ω are connected in para lied with a source of 6 volt. Find the current flowing through the circuit.

19. What is an Ammeter? How is a Galvanometer changed into an ammeter? Also state how an ammeer is connected in an electrical circuit?

Ammeter is an instrument which measures the amount of current passing through a circuit:

CONVERSION OF GALVANOMETER INTO AN AMMETER:

A galvanometer can be converted into an ammeter by connecting a very small resistance called shunt in parallel with the coil of the galvanometer. By doing so most of the current passing  through the galvanometer is bi-passed through the shunt and the range of the instrument to measure current is increased.

CONNECTION OF AMMETER IN CIRCUIT:

An ammeter is always connected in series in an electrical circuit.

20. Define the following:

(i) Electronics
(ii) Doping
(iii) Rectification

(i) ELECTRONICS:

Electronics is the branch of physics which deals with utilization and control of electrons in electron emitting devices designed for various purposes.

(ii) DOPING:

The method of increasing the electrical conductivity of silicon or germanium, by adding in them small amounts of trivalent element like Indium or a element like Arsenic which is called impurity, is known as Doping.

(iii) RECTIFICATION

Rectification is the phenomenon of converting A.C. current to D.C. current

It is done by p-n junction diode.

21. The half-life of Radium is 1600 years. Find the amount of Radium left after 4800 years, if its mass is 60g.

22. How much amount of heat is required -to raise the temperature of 800 g of Iron through 50°c. (Specific heat of iron = 499.8 J/kgºc)

Data: Mass of Iron m = 800 gms

SECTION C (DETAILED – ANSWER QUESTION)

Suppose the initial velocity of a moving body is “W’. It increases with a uniform acceleration “:a” and in a time interval “t” changes into a final velocity “V,”. Let the distance covered during this period is “

23.(b)State Newton’s Second Law and third Law of Motion and derive: F = ma.

NEWTON’s THIRD LAW OF MOTION:

It states that for every action there is an equal and opposite reaction.

F=-F

NEWTON’s SECOND LAW OF MOTION

It states that when a force acts on an object, it produces an acceleration in its own direction, which is directly proportional to the magnitude of force and inversely proportional to the mass of the object

Mathematically:
A x F (for a constant mass)
and a x 1/m (for a constant force)
Combining the above two relation

Where K is constant
In S.1.units force F is measured in Newton or Kg x m/s²
Then K = 1
and the relation becomes

23.(c)Draw a Ray Diagram of a Compound Microscope and describe its working.

WORKING:

The object is placed between F and 2F of the objective. It forms a real, inverted image called 1stImage AI B/. The eyepiece is brought close to it so that it comes within its focal length.

Then the first image AI BI acts as an object and forms a virtual erect and highly magnified final image A” B”.
The magnification can be varied by different objectives

24.(a)State Boyle’s Law & Charles’ Law. Also derive PV = nRT

24.(b)Write two differences between:

(i) Stress and Strain
(ii) Kinetic Energy and Potential Energy

STRESS

(i) It is an opposing force that resists a change in shape and defined as the force per unit area
(ii) Street = Force / Area
(iii) Unit of stress is N/m²

STRAIN

(i) It is defined as the fractional deformation produced in a body due to a certain stress.
(ii) Longitudinal strain = Changein length Originallength
(iii) Strain has no unit

Potential Energy

(i) Energy possessed by a body by virtue of its position or change of shape is called potential energy.
(ii) It increase with increase in height and it is given by the PE= mgh

Kinetic Energy

(i) The energy possessed by a body due to its’ motion is called kinetic energy
(ii) It increases with increase in velocity and -given by the formula. K.E. = ½ mv²

(i) Friction between feet and ground helps in walking. When we push the ground backwards, the friction gives a reaction in forward direction and-we move forward.
(ii) friction helps the nail to stay in wood and also to tie a knot

(i) Friction produces heat in various parts of machine and useful energy is wasted asheat energy.
(ii) Cars, buses and trains lose part of energy inovercoming friction.

Friction between joints of our body makes movement very difficule.

25.(a)With the help of a labeled diagram explain the construction and working of an Electrical Bell

It works on the principle of Electro magnet. Whenever magnetized at attract an armature and the hammer at its end strikes a bell

CONSTRUCTION:

It consists of a horseshoes magnet on which a wire is wound. One end of the wire is connected to the terminal T¹ and the other end to a spring attached to an iron strip called armature. The armature bears a small rod at the end of which is a hammer. A very light spring is attached to a contact adjusting screw. Which is joined to the second terminal T² by a wire. The electric circuit is completed through the mains or a battery.

WORKING:

When the push button is pressed the electric circuit is completed and the armature is attracted towards the electromagnet as it moves towards the magnet the hammer strikes the bell. But the small spring gets detached from the screw and the circuit is broken. The magnet is demagnetized and the armature moves back again the circuit is completed armature again moves towards the magnet and hammer . strikes the bell. This process continues and the bell rings

25.(b) Define the following:

(i) Surface Tension
(ii) Viscosity
(iii) Orbital velocity
(iv) Couple

Surface Tension:

The inter molecular attractive forces give rise to a net force that act along with surface of a liquid. This causes the surface to behave like a stretched membrane.

Viscosity:

Viscosity is the force that arises due to force of friction between different layers of a fluid. This force resists easy flow of the fluid.

Orbital velocity

It is the velocity of a satellite which moves around the earth at a specific height

Couple:

Two equal but opposite parallel forces which act at different points on a body make together a couple.

25.(c) Write two differences between:

(i) p-type substance and n-type substance
(ii) Fission reaction and Fusionreaction

Posted on December 16, 2015 in 10th Class 2013 Karachi Board Past Papers