# Physics Solved Past Paper 10th Class 2011 Karachi Board

SECTION ·A’ MULTIPLE CHOICE QUESTION

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

(i) Amplification can be obtained by:
(b) Transistor
(c) P.N.Junction
(d) Capacitor

(ii) If V=10 mIs, t=5 sec, S will be:
(a) 15m
(b) 5m
(c) 2m
(d) 50m

(iii) The elements having atomic Number greater than 82 are
called:
(a) Semiconductor
(b) Conductor
(c) Insulator

(iv) The substance placed between the conductor plates of
the capacitor is called:
(a) Dielectric
(b) Capacitor
(c) Insulator
(d) Resistance

(v)In S.I.Unit value of Gis:
(a) 6.67 x 1011Nm2/Kg2
(b) 6.67 x 10.11Nm2/Kri
(c) 6.76 x 1011Nm2/Kg2
(d) 6.76 x 10.11 Nm2/Kg2

(vi)Maximum beat frequency that human ear can detect is:
(a) 6
(b) 7
(c) 5
(d) 10

(vii)Unit of light intensity is:
(a) N/m2
(b) Volt
(c) Candela
(d) Joule

(viii)Which of the following is same as Kg.m/s2
(a) joule
(b) Newton
(c) Pascal
(d) Watt

(ix)Loudness of sound depends upon:
(a) Area of vibration
(b) Amplitude
(c) Frequency
(d) All of them

(x)Rate of motion in specific direction is called:
(a) Speed
(b) Velocity
(c) Acceleration
(d) Power

(xi)Equivalent weight of 10 kg is:
(a) 98 N
(b) 980 N
(c) 100 N
(d) 196 N

(xii)Which of the following never gives a real image:
(a) Plane mirror
(b) Concave mirror
(c) Convex mirror
(d) Human eye

(xiii)One micro metre is equivalent to:
(a) 10·3m
(b) 10-6m
(c) 10·9m
(d) 10·12m

(xiv)Refractive index of water is:
(a)1.5
(b) 1
(c) 2.4
(d) 1.33

(xv)Human eye is similar to:
(a)Microscope
(b) Telescope
(c) Camera
(d) Periscope

(xvi)Kitab-AI-Manazir is written by:
(a) Ibn-al-Haitham
(b) Yaqoob-al-Kindi
(c)AI-Beruni
(d) Moosa Kawarzmi

(xvii)Acceleration of 1kg ball for downward motion is:
(a) 9.8 m/s2
(b) -9.8 m/s2
(c) 1 m/s2
(d) 98 m/s2

2. Define physics and write down only the names of four branches.

3. A body weighting 25 N is placed on a wooden plank. How much force is required to set it in motion if the co-efficient of friction between plank and the body is 0.4

4. Define Work and write down its two formulad.

WORK:

Work is said to be done when a force acts on a body and moves it through some distance.

FORMULAE OF WORK:

(1) When force acts in the direction of motion:
W = F x S
(2) When force acts an angle 9 with the direction of motion:
W= F s Cos 0

5. Define the following:
(i) Limiting frictions
(ii) Inertia
(iii) Power

(i) LIMITING FRICTIONS:
If a body is made to slide over the surface of another its motion is opposed by a force due to the roughness of the two surfaces. The maximum· of this force is called Limiting Friction.
(ii) INERTIA:
Inertia is the tendency of an object to resist a change in its state of rest or motion.
(iii) POWER:
Power is defined as the rate of doing work.

6. Define machine and write down the names of four simple machines

DEFINITION: A machine is a device which helps to do work in a convenient manner. Four simple machines are:

(i) Lever
(ii) Pulley
(iii) Wheel and Axle
(iv) Screw

7. What is Transistor. Write its two advantages

TRANSISTOR:
A transistor is a semi-conductor having a thin central layer of one type of semiconductor sand witched between two relatively thick pieces of the other type. It is used as an Amplifier.

(i) It is exceedingly small and light
(ii) It can be used with very small potentials.

8. Draw a labeled diagram of an electric bell

9. Write down three differences between Mass and Weight.

10. A body of 20 Kg is moving with a speed of 15 m/s. Find it momentum.

11. Hlw much hear is required to raise the temperature of 100kg of Iron through 10ºc? (Specific hear of iron is 499.8 J/lgºC

12. Define the following:

(i) Dispersion of Light
(ii) Magnification
(iii) Focal length of Concave mirror

(i) DISPERSION OF LIGHT:
The splitting up of white light into its constituent colours is called Dispersion of light.
(ii) MAGNIGICATION:
The ratio between image height to Ibject height is called

(iii) FOCAL LENGTH OF CONCAVE MIRROR:
The distance between principal focus and the pole of a concave mirror is called its focal length and denoted by f. It is positive

13. Draw the ray diagram for the formation of image in a plane mirror.

14. Calculate amount of current passing through an electric heater if it takes 1800 C of charge to heat in 3 min

Data: Charge q = 1800 Coulomb
Time t = 3 min
= 3 x 60 = 180 Sec.
Current I= q/t
1= 1800/180 = 10 Ampere

15. Prove that V = ƒλ

16. Find the Focal length of a concave lens if P = 5cm, q = 10cm and the image formed is virtual

17. A stone is dropped from a tower .It reaches the ground in 5 seconds.calculate the height of the tower

18. Define resolution of vector & write down . two formulae of rectangular components

RESOLUTION OF A VECTOR:

The process of splitting up of a vector into components which are rectangular to each other is called Resolution of a vector.

Horizontal Component: Fx= F Cos e
Vertical Component: Fy= F 5in e

19. Describe Quantum theory of light.

QUANTUM THEORY OF LIGHT:
(i) It states that light is emitted from a source in the form of packets of energy called photons.
(ii) The photons are not material particles like Newton’s light corpuscles.
(iii) The energy of a photon depends on its frequency. Greater the frequency, more will be its energy.

The frequency of violet light is twice that of red light. So energy of a photon of violet light is double that of red light.

20. A Sitar string vibrates at 400Hz. What is . the time period of this vibration?

Data: Frequency f = 400 Hz
Time period t = ?
SOLUTION: Formula:
T = 1/f
T = 1/400
T = 0.0025 second

21. Define the following:
(i) Half life of radio active elements.
(ii) Doping
(iii) Magneticfield

(i) HALF LIFE OF RADIO ACTIVE ELEMENTS:
The half life of a radioactive element is the time interval in which half of its atoms decay or change into daughter elements. It is the half life of the parent element.
(ii) DOPING: Please see Q.no.23(c)(iv)of 2012
(iii) MAGNETIC FIELD:
Magnetic Field is the space surrounding a magnet, in which its magnetic effect is felt, is called Magnetic field. It is a region in which the magnet can exert its magnetic force.

22. In a nuclear reaction 9 x 1010J of energy is released due to conversion of mass into energy. How much mass has been converted \ into energy?(Speed of light is 3x 10em/s)

Data: Energy E = 9 X 1010 Uoule
Speed of light C=3 x 108 m/sec
Mass m =?

SOLUTION:

23.(a) Derive the equation S = Vit + ½ at²

23.(b) Draw the Ray diagram of a compound Microscope and write its working.

23.(c) Define Radio isotopes and state its one use in agriculture and two uses in medicine

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.
USES IN AGRICULTURE:
A radio-isotope is used to determine the optimum amount of fertilizers and other nutrient intake by plants.
USES IN MEDICINE:
(i) RADIO STRONTIUM: Radio strontium is used in the treatment of internal hemorrhages and wounds.
(ii) PHOSPHORUS 32: Phosphorus 32 is used to locate precisely the position of tumor in brain.

24.(a) State Boyle’s law, Charles’ Law and Pressure Law. Derive PV = nRT.

24.(b) Draw Ray diagram for image formed by Concave mirror & write its characteristics.

Between the centre of curvature and the principal focus:

24.(c) What is Radar? Write its three uses

Radar is an electronic device for Radio Detection and Ranging by sending very high frequency electromagnetic waves, which strike an obstacle and come back.

(i) It is used as a navigational aid on ships and aero planes.
(ii) Radar is also used for air traffic control, weather observations and storm warnings.
(iii) In war times Radar detects the energy planes flying in its range

2S.(a)Define Fission reaction. Write down its equation & draw diagram for chain reaction.

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.

25.(b) Define the following:
(a) Ampere
(b) Volt
(d) ohm

(i) AMPERE: Ampere is the unit of current If one coulomb charge flows across any cross section of a wire in one second, the current flowing is one ampere.
(ii) VOLT: The potential difference between two points is one volt if the amount of work done by 1 coulomb charge in moving from one point to another is one Joule.
(iii) FARAD: It is the unit of capacity. The capacity of a capacitor is said to be one Farad, if it stores a charge of 1 coulomb when the potential difference between the plates is 1 volt.
(iv) OHM: Ohm is the unit of resistance. If the potential difference across the ends of a conductor is one volt and the resulting current passing through it is one ampere, then, the resistance offered by the conductor is one ohm

25.(c) State the following laws/principles