# Physics Solved Past Paper 10th Class 2014 Karachi Board

SECTION “A” (COMPULSORY)(M.C.Q.)

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

(1) Which on e of the following has maximum value of
refractive index?
(a) Ruby
(b) Crownglass
(c) Quartz
(d) Diamond

(2) Production of beats is due to the ——-of sound waves:
(a) Interference
(b) Reflection
(c) Diffraction
(d) Refraction

(3) The branch of physics concerned with highly ionized
atoms is called —— Physics:
(a) Atomic
(b) Nuclear
(c) Plasma
(d) Nuclear State

(4) The Unit of co-efficient of friction (~L)is:
(a) Newton
(b) Joule
(c) Newton metre
(d) None of these

(5) The waves produced by a vibrating body in air are:
(a) Longitudinal waves
(b) Transverse waves
(c) Electronegative waves
(d) Magnetic waves

(6) It always gives virtual image:
(a) Concave lens .
(b) Convex Mirror
(c) Plane Mirror
(d) All of them

(7) The viscocity of Ethanol is:
(a) 0.019
(b) 0.1
(c) 1.000
(d) 0.801

(8) If frequency of a pendulum is 10 Hz, then time period will be:
(a) 1 sec.
(b) 10 sec.
(c) 0.1 sec.
(d) 0.01 sec.

(9) Water has maximum density at:
(a) O°C
(b) _4°C
(c) 4°C
(d) 100°C

(10) 1 Mega metre = ——— metres.
(a) 1012
(b) 109
(c) 106
(d) 1015

(11) If P = 15 cm, q = 30 ern, the magnification is ——–:
(a) 2
(b) 1/2
(c) 45
(d) 15

(12) Latent heat of vaporization of water is:
(a) 3.36 x 105 J/kg
(b) 2.26 x 105 J/kg
(c) 2.26 x 106 J/kg
(d) 2.26 x 10.6 J/kg

(13) Right hand rule is introduced by:
(a) Maxwell
(c) Oersted
(d) Ampere-

(14) Rainbow appears due to:
(a) Absorption of light
(b) Dispersion of light
(c) Refraction of light
(d) Reflection of light

(15) The mass of our galaxy is:
(a) 2x1043kg
(b) 2x1050kg
(c) 6 X 1024 kg
(d) 7 x 1022 kg

(16) Which of the following is used for the study of thyroid glands?
(a) 1-132
(b) P-32
(c) Na-24
(d) CD-60

(17) Rechargeable cell is called ——— cell.
(a) Daniell
(b) Secondary
(c) Primary
(d) voltaic

(2) Write down S.I.U. for the following:

(i) Viscosity
(ii) Strees
(iii) Torque
(iv) Temperature
(v) ‘Momentum
(vi) Input

(3) How much energy will be released when 20 gm mass is completely transferred to energy by Einstein’s Euation?

Derivation of V = V + at

(5) Write down three differences between Transverse and longitudinal waves.

(6) A gun of mass 10 kg fires a bullet of mass 0.05 kg with a speed of 200 m/s. Calculate velocity of recoil of the gun

(7) Derive Mechanical advantages Formula for Inclined Plane.

Definition of Machine

A machine is a device, which helps in doing work in a convenient manner

Six Simple machines:

All machines consist of different combination of six simple machines, which are.

(i) Liver
(ii) Wheel and Axle
(iii) Pulley
(iv) Inclined plane
(v) Wedge
(vi) Screw

Inclined plane

is a simple machine, which is just a plane strong sheet, makina an anale e with the qround.

The sheet AB has its end ‘B’ lying at height h with respect to horizontal surface and making angle e with it.

In order to raise the weight ‘W’, an effort ‘p’ is applied parallel to the inclined plane upwards.

When this effort ‘p’ is applied through a distance ‘L’ the load is raised to a height ‘h’ above the ground

If friction is neglected, then
Out put = In put.
Out put = weight x height raised.
= w x h

(8) A 5m long beam pivoted into a wall, a force of 100 N is applied vertically at the Far end of beam. Find the torque produced.

(9) Define: (i) Power (ii) Spectrum (iii) Newton

(i) Power:

(ii) Spectrum:

When sunlight is passed through a prism in a dark room, a band of 7 colours is obtained on the wall or screen. Its is called spectrum. Colours are VI BG

(iii) Newton

It is the unit of force in S.1. system. A force which produces an acceleration of 1m/s² a mass of 1 Kg is called one Newton force

(10) How can we convert a Galvanometer into Ammeter and Voltmeter? (Show only by labeled diagrams).

Conversion of Galvanometer into Ammeter:

11) Find the amount of heat required to convert 10kg ice O°C into water without changing the temperature while latent heat of fusion of ice 336000 J/kg.

(12) Write down any three differences between alpha and beta rays?

(13) Show the image formation and characteristic by Convex Mirror with the help of ray diagram.

(14) The focal length of a convex lens is 20 ’em, If the image formed by it is twice in size, find the position of the object

Data:                Lens is convex
Let size of object = 1 cm            Size of Image given = 2
Focal length f = 20 cm               Object distance p = ?

SOLUTION:

(15) Write three differences between Forward and Reverse biased.

(16) Calculate the amount of work. done in carrying a charge of +25 ∪ C from A to B. If A is at a potential of ·60 V and B is at 10 V.

17) Define : (i) Resonance (ii) Inertia (iii) Specific Heat

(i) Resonance:

Resonance is the response of an object to a periodic force acting on it having time period same as natural time period of the object. The object begins to vibrate with greater and greater amplitude

(ii) Inertia:

Inertia is the tendency of an object to resist a change in its state of rest or motion

(iii) Specific Heat

Specific heat is defined as the quantity of heat required to change the temperature of unit mass (1 Kg) of a substance by one degree centigrade.

(18) Describe any three laws of fusion

Laws of fusion:

(i) Every substance changes its state from solid to liquid at a particular temperature at normal pressure.
(ii) During change of state the temperature remains constant.
(iii) One Kg. of a solid needs a definite heat to change from solid to liquid, called latent heat of fusion.

(19) Define Electric Motor and Write down two faetors on which its speed depends

Electric Motor is a device which converts electric energy into mechanical energy.

The speed of an eclectic motor depends on

(i) Magnitude of current through the rotor.
(ii) Magnetic field strength of the permanent magnet

(20) Two bodies of Masses 5 kg and 4 kg are attached to the ends of a string which passes over a friction less pulley such that two bodies hang vertically. Find the acceleration of the bodies.

Data:

Mass of body A = m¹ = 5 kg
Mass of body B = m²= 4 kg
G = 10 m/s²                Acceleration a = ?

(21) Write down 3 uses of laser technology.

Uses of laser technology:

(i) Laser are used for medical treatment of various organs of body.
(ii) Lasers are used in the defense of a country.
(iii) Lasers are also used in metallurgy, metal cutting etc.

(22) 20 waves per second pass through a point on the surface of the pond. Calculate the wave-length if. the velocity of wave is the 3.5 ms¹,

SECTION ‘C’ (DETAILED – ANSWER QUESTIONS

23.(a)With the help of V², V² and s derive the equation of motion

(b) What is bimetallic strip? Describe its three applications.

Bimetallic Strip:

If strips of two deferent metals like Iron and Brass are joined length wise and riveted together the resulting joint strip is called Bimetallic Strip

(i) Bimetallic thermometer

This thermometer consists of a bimetallic strip in the form of a long spiral. Its one end is fixed and the other and is firmly joined to a pointer which moves over a scale which is calibrated to measure temperature. When the temperature rises, the spiral-turnings are more tightened because of the different amount of expansion of the strips forming the given bimetallic strip. This results in the movement of the pointer on the calibrated scale which reads the temperature directly

(ii) Bimetallic thermostat:

A bimetallic strip can be incorporated to an electrical circuit to serve as a thermostat, a device to control the temperature. Suppose that a bimetallic strip is connected to an electric room heater. When the current flows through the heating element of the heater, its temperature rises and attains a value at which the bending of the bimetallic strip is so large that the electric contract is broken and the current ceases to flow. This result in the fall of temperature which reaches such a value that the bimetallic strip straightens to close the circuit again. The heating element is switched on and the bending of the bimetallic strip starts again the process of on and off is repeated and the temperature is controlled that is temperature range of the heater is fixed.

(iii) Fire alarm

A very useful application of a  bimetallic strip is a fire alarm. One end of the bimetallic strip is fixed and the other is free. A 6 volt battery is connected between a metallic contact and the fixed end of the bimetallic strip through an Contact electric bulb or an electric bell. The metallic contact is kept just above the free end of the bimetallic strip.

(c) With the help of prism, draw solar spectrum of dispersion of light.

DISPERSION

Sunlight consists of different colours was first investigated by Newton.

A beam of sunlight was allowed to enter a darkroom through a hole in the window. A prism was placed in the path of the beam of light. A band of various colours was produced on the wall. This band of colour is known as a solar spectrum and the phenomenon is called dispersion of light. Sun light is a combination of various waves. When they pass through a glass prism refraction takes places. Waves of higher frequencies bend more than those of lower frequencies. Thus different waves with different wavelengths and frequencies in the visible light region would separate in the shape of a spectrum of colours. The shortest wavelength visible to the human eye is violet and its deviation is the greatest. The longest visible wavelength is red colour and its deviation is the least.

24.(a) Define Nuclear fission Reaction Write down its equation and explain chain Fission reaction

NUCLEAR FISSION REACTION:

The splitting of a heavy radio active nucleus into fragments with the emission of energy when bombarded by a neutron is called Fission.

EQUATION OF FISSION:

The energy released is due to the fact that, when a nucleus splits into fragments, the total mass of the fragments is less than that of the nucleus . This mass difference according to Einstein’s mass energy relation appears as energy

CHAIN REACTION:

In a fission reaction each nucleus emits about two to three neutrons. These neutrons collide with the other uranium nuclei and cause fission in them. The nuclei which undergo a fission reaction will emit neutrons. These neutrons will produce further fission in other nuclei. This process continues, more and more neutrons are produced and a larger amount of energy is released. This is called a nuclear chain
reaction

(b) Define Resolution of Vector and resolved a vector into its components.

Resolution Vectors:

The process of splitting up of a vector into its components which are rectangular to each other, is called resolution of vectors.

Suppose a force F acts on a body in such a manner that it makes an angle e with the Xaxis. From the point A a perpendicular AB is dropped on the X-axis. Then as OB is o along X-axis it represents.

The x-component of the force F and as AB is parallel to Y-axis it represents the Y-component of the force F. From the rt. Angled ABC:

(c) Draw the diagram of defects of eyes. Describe short sightedness and long sightedness

The main defects of human eyes are (i) Short sightedness and (ii) Long sightedness.

(i) Short sightedness

In this defect the eye cannot see distant object clearly. The reason is that the image is formed in front of the retina, because the either the eyeball is too elongated or the focal length of eye lens is too short.

Remedy:

Spectacles of concave lenses can connect short sightedness.

(ii) Long sightedness

In this defect the eye cannot see near objects clearly. The reason is that the eye ball is too short or the focal length of the eye lens is too long. As such, the image is formed behind the retina.

Remedy:

Spectacles of convex lenses can correct long sightedness.

25.(a) Define Kinetic Energy & derive the equation K.E=½ mv²

DEFINITION:

Potential energy is the energy possessed by a body by virtue of its position or change of shape

KINETICENERGY:

The energy possessed by a body due to its motion is
called Kinetic Energy. K.E. = ½ mV²

DERIVATION OF FORMULA:

Suppose a body of mass m is at rest on a frictionless floor. en a force F is applied the body covers a distance of 5 meter and attains a final velocity V

(b) Draw the diagram of nuclear reactor and describe the importance of boron rod

IMPORTANCE OF BORON RODS:

The boron rods are very important in the reactor as they absorb the fast moving neutrons in fission reaction. They are called control rods. Boron rods are insected in the path of neutrons according to the previously calculated need of energy, in the peace ful fission process. The released energy is converted to electrical energy

(c) With the help of figure write the four rules of reflection of rays of light by concave mirror.

Rays reflected from a concave mirror follow certain rules which are given as follows:

(i) A ray coming parallel to the principal axis is reflected through the principal focus.

(ii) A ray which is coming through the principal focus Is reflected parallel to the principal axis

(iii) A ray which is coming through the centre of curvature is reflected back along the same path.

(iv) A ray incident on the pole at an angle e with the principal axis is reflected back at the same angle

Posted on December 16, 2015 in 10th Class 2014 Karachi Board Past Papers