# Physics Solved Past Paper 10th Class 2012 Karachi Board

SECTION ‘A’ MULTIPLE CHOICE QUESTION

1. Choose the correct answer for each from the given options: 2. Define scalar and vector quantities with two examples of each:

SCALARS:

Scalars are those physical quantities which can be easily understood by their magnitude expressed in suitable units. They do not require any mention of direction.
E.g. Mass; Speed

VECTORS:

Vectors are those physical quantities which require, not only magnitude but also direction for their complete description.
E.g. Velocity: displacement.

3. Define Equilibrium. Write the names of three states of equilibrium. Give one example of each:

Definition:

If a body maintains its state of rest or of uniform motion, and does not rotate about its axis of rotation, under the influence of force, then. it is said to be in- Equilibrium

There are the three states of Equilibrium

(i) Stable Equilibrium
E.g. A chair on floor. A balancing toy
(ii) Unstable Equilibrium
E.g. A pencil standing vertically An acrobat on rope
(iii) Neutral Equilibrium
E.g. A ball lying on floor; A meter rod suspended by a nail passing through a hole at its centre of gravity

4. With the help of trigonometric ratios, find the magnitude of horizontal and vertical components of a vector.

5. A car is moving on a straight road at a speed of 5 m/s. It is accelerated at 3 m/s². Calculate its velocity after 4 seconds.

Data: Vi = 5m/sec a = 3m/s² t = 4 seconds Vf = ?

Solution:

Vf = Vj + at
Vf = 5 + (3×4)
Vf = 5 + 12
Vf = 17 m/sec

6. Write down three contributions of AI-Beruni in the field of science.

CONTRIBUTION OF AL-BERUNI:

(i) He measured the circumference of Earth during his travels, at Pind Dadin Khan
(ii) He wrote the famous book Qanoon AI Masoodi about phases of moon and the movement of the known planets.
(iii) He also determined the densities of metals.

7. State Pascal’s principle & write its three uses in daily life:

PASCALS PRINCIPLE:

It states that “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”

USES OR APPLICATIONS OF PASCALS PRINCIPLE:

(i) In Hydraulic Brake system:

A small push on brake pedal becomes a great pressure by transmission through brake oil. This pressure acts on brake shoes of wheels and a vehicle stops.

(ii) Hydraulic Press:

A small pressure on piston of the narrow limb becomes many times greater, by transmission through the liquid and acts upwards on the broader piston. This pressure causes loose cotton to become compact bale

(iii) Hydraulic Lift:

The same principle used in Hydraulic Press, lift a vehicle on the broader piston of Hydraulic lift.

8. Define the following Laws:

(i) Boyle’s Law
(ii) Law of conversation of momentum
(iii) Newton’s third Law of Motion

(i) Boyle’s Law:

It states that at constant temperature, the volume of a given mass of gas in universally proportional to pressure.

(ii) Law of Conservation of Momentum:

It states that “the total momentum of an isolated system which is not acted upon by an external force, always remains constant.”

(iii) Newton’s Third Law of Motion:

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

9. How much amount of heat is required to raise the temperature of 100 gm of water from 20°C to 80°C. (Specific heat of water is 4200 Joules)

10. What is Newton Corpuscular Theory of light.’ Write down two phenomena which support this Theory:

Newton corpuscular theory of Light:

(i) Light consists of minute particles \called Corpuscles, which come out from light source and travel in straight lines.
(ii) Reflection is due to rebounding of these corpuscles from a mirror and Refraction is due to entering of corpuscles into the second medium and change of speed.
(iii) Formation of shadows is due to blocking of the corpuaclas’ by ‘an opaque object

Supporting Phenomena:

(i) Max Plank’s Quantum theory based on tiny packets of energy, supported Newton’s Corpuscular theory.
(ii) Formation of shadows proved rectilinear propagation of light and rebounding of corpuscles from mirror proved reflection of light.

These phenomena support this theory

11. A force of 588 N acts on a box to move it at a distance of 4m in 40 Seconds. Calculate the power

12. Define the following:
(i) Alternating Current (A.C)
(ii) Electric Field
(iii) Electrostatic Induction

DEFINITIONS:

(i) Alternating Current (A.C):

A current which changes its direction many times a second is known as alternating current

(ii) Electric Field

Electric field due to a charge is the spare around that charge in which its influence is felt by another charge is called as test charge

(iii) Electrostatic Induction

The production of opposite charge on a neutral body when a charged body is brought close to it is called Electrostatic Induction

13. Write three uses of concave mirror:

Uses of spherical mirrors:

(i) A concave mirror is used in a microscope to illuminate the object in reflecting tales cope-it is used as objective
(ii) Concave mirror is used by doctors for medical examination of ear, nose, throat and eyes in ophthalmoscope.
(iii) Concave mirror is used in searchlights and spotlights, and in head light in automobiles.
(iv) Convex mirror is used at driving seat in cars and buses to have the rear view of traffic.

14. Write three differences between α – rays and β – rays.

15. Derive the relation w = I² Rt.

16. What is a Transistor? Describe two types of transistor with the help of diagrams

TRANSISTORS:

A transistors is a three pieces semi-conductor having a thin central layer of one type of semi conductor, sandwiched between two relatively thick pieces of the other type. It is used as an amplifier

Type of Transistors:

The central part in each, is called ‘base’ and the pieces at either side are called emitter (e) and the collector (c).

17. Find the resistance of a bulb, if 0.6 A current is passing through the bulb and the potential difference across the bulb is 90 Volt.

18. Define the co-efficient of Linear Expansion and co-efficient of Volumetric Expansion.Write the relation between them:

Co-efficient of Linear Expansion:

It can be defined as the fractional increase in length of a
rod or wire, per unit change in temperature. It is denoted by α

Coefficient of Volumetric Expansion:

It can be defined as the fractional change in volume per
unit change in temperature. It is denoted by Beta β

Relationship between alpha (α) and beta (β)

Beta is three times alpha .
β=3α.

19. The radius of curvature of a concave mirror is 20 cm. where should an object be placed so as to get its real image magnified twice?

Data: Radius of curvature R = 20 cms Image is real
Magnification M = 2              Object distance p = ?

20. Write down three characteristics of the image formed by a plane minor.

21. A force of 100 N acts at an angle of 60° with the horizontal. Find its horizontal and vertical components, where Cos60° = 0.5 and Sin 60° = 0.866

22. Write down any three characteristics of resistances connected in parallel

Resistance connected in Parallel:

Characteristics:

(i) There are different paths for the flow of current and the total current and the total current is distributed in these paths

(ii) Potential difference across each resistance is the same as that of battery

(iii) Equivalent Resistance of the parallel combination is less than the least resistance. Equivalent resistance is given by

SECTION ‘C’ (DETAILED – ANSWER QUESTION)

23.(a)Define potential energy & kinetic energy and derive the equation K.-E= ½ mv².

(b) Define the capacity of a capacitor. Write down three factors upon which capacity of a capacitor depends

Capacity of a Capacitor:

If a capacitor holds a charge q at potential difference V between the plates, then the ratio charge q to the potential difference V

i.e. q/v is a constant called Capacity of the Capacitor and denoted by ‘C’ or C = q/v .

Factors on which capacity depends:

(i) Area of the plates, greater the area, greater is the capacity’
(ii) distance between the plates. lesser the distance, greater is the capacity
(iii) Nature of the medium between the plates. greater the capacity if the medium is Mica or oiled paper rather than air.

(c) Define the following:

(i) Proton: The particle inside the nucleus of an atom, having positive charge is called Proton.
(ii) Echo: The sound heard after reflection from a surface is called Echo.
(iii) Nuclear Reactor: A system used to obtain is controlled amount of heat from nuclear fission is called a Nuclear reaction.

(iv) Doping: Please see Q.no.20(ii) of 2013

24.(a)Define Coulomb’sLaw

Derive the equation:

COULOMB’s LAW:
States that “The Magnitude of Electrostatic force between two point changes is directly proportional to the product of the magnitude of changes, and inversely proportional to the square of the distance between them? (i) Co-GO
(ii) 1-131
(iii) P-32

Atoms of same element which differ in Mass Number are Isotopes. Those isotopes which are radio active and emit different radiations are called Radio Isotopes

Co-GO is used to treat cancerous tumors inside the body.
1-131 It is used for the study of thyroid glands in human body
P-32 is used to locate precisely the position of tumor in brain

(c) Define loudness of sound. Write 3 factors on which the loudness of sound depends

Loudness of Sound:

Loudness is that property of sound which enable3s us to distinguish between a faint and a loud sound. It depends on the intensity of sound waves

Factors on which loudness depends:

(i) Area of vibrating body:

The larger the area of the vibrating object, the louder is the sound produced e.g. a drum gives louder sound than a dholes.

(ii) Amplitude of the vibrating body:

If the amplitude of vibrating object is larger or greater, louder sound is produced. E.g. A drum struck strongly makes its membranes vibrate with greater amplitude, and produces louder sound.

(iii) Distance of the source of sound:

If the lister is far away from the source of sound, faint sound is heard, when the source of sound is near, loud sound is heard.

25.(a)Derive equation 2aS = yf²- vi²

(b) Draw a neat labeled ray diagram of simple microscope.Write down the characteristics of the image formed by it and the formula of its magnifying power

Characteristics of Image by Simple Microscope:

(i) The image is virtual and exact.
(ii) It is highly enlarged.
(iii) The image is formed towards the object itself

Formula of Magnifying power:

(c) Define the following:

(i) Frequency: Frequency is the number of vibration executed by a vibrating body in one second, denoted by ;f
(ii) Time Period: It is the time required to complete one vibration or oscillation. It is measured in seconds
(iii) Pitch: It is that property of sound by virtue of which a shrill sound and a flat sound can be distinguished

Posted on December 17, 2015 in 10th Class 2012 Karachi Board Past Papers