Federal Board HSSC-I (2012)
PHYSICS
Time: 25 Minutes Marks: 17

Note: Section-A is compulsory and comprises pages 1-2. All parts of this section are to be answered on the question paper itself. It should be completed in the first 25 minutes and handed over to the Centre Superintendent. Deleting/overwriting is not allowed. Do not use lead pencil.

SECTION — A (Marks 17)

Q.1 Circle the correct option i.e. A/B/C/D. Each part carries one mark.

• The dimension of gravitational constant "G" is  __  .
  

A. M¹L³1^-1 
B. M^-1L³T^-2
C. M²CL¹T^-3
D. M^-2L^-1T^-3

• The S.I unit of time is__________.     
  

A.60 min
B. Cesium SeC.
C. Krypton-86     
D. 60 SeC.

• A 1 kg block slides down a smooth inclined plane whose height is 5 m. The velocity of the body at the bottom is _________
  

A.ms^-2     
B. 5ms^-1
C. 9.8ms ^-2            
D. 7ms^-1

• What is the angle between the two vectors?  = 5ȋ + ĵ and  = 2ȋ + 4ĵ?
  

A.66°     
B. 52°
C. 25°     
D. 33°

• A ball is thrown above the horizon, making an angle of 30°. The height attained by the ball is 11.5 m. The  launching         velocity of the ball is_________
  

A.20ms^-1          
B. 60ms^-1
C. 30rns^-1
D. 45ms^-1

• A brick of mass 2 0 kg is dropped from a rest position 5.0m above the ground. Its velocity at a height of 3.0m above the ground will be
  

A.3.6rns^-1              
B. 8 6ms^-1 
C. 6 3ms^-1 
D. 7.8ins^-1 

• The expression for spinning frequency to create artificial gravity in satellite is
  

• A gramophone record turntable accelerates from rest to an angular velocity of 45.0 rev min^-1  in 1.60s. The average angular acceleration is
  

A. 29.5rad s^-2        
B. 2.95rad s^-2 
C. 2.95rev s^-2       
D. None of these

• The expression for terminal velocity is  
  

A.Vt =           
B. Vt =
C. vt =          
D.  vt=

• The instantaneous P.E of spring mass system is given by

A. P. EMAX=kx²₀
B. P.E=kx²₀
C. P.E=k² 
D.  P.E=kx² 

• A simple pendulum is 50.0cm long. Its frequency of vibration at a place where g = 9.8ms^-1is

A. 0.70 Hz 
B  7Hz
C. 6.2 Hz 
D. 10 Hz

• The temperature at which the velocity of sound in air is two times its velocity at 10°C is
  

A. 1321 K               
B. 1213 K
C. 1132 K               
D. 1231 K

• For destructive interference path difference between two sound waves is
  

A. S =nλ+λ
B. S=(2n+1)
C.  S=(2+)n
D. S=nλ

• The frequency for nth mode of vibration for stationary longitudinal waves in a pipe open at both ends is

A.fn =
B. fn =
C. f n=
D.  fn =

• In case of X-ray diffraction by crystal the wavelength can be found by using the equation

A. dsinθ = nλ
B. 2dsinθ = nλ
C. 2dcosθ = nλ
D. dcosθ = nλ

• An astronomical telescope having magnifying power of 5 consist of two thin lenses 24 cm apart. The focal length of the lenses is
  

A.4cm   
B. 20cm
C. 16cm  
D. None of these

• An ideal reversible heat engine has_______.
  

A. 100% efficiency
B.  Highest efficiency
C.  Art efficiency which depends on the nature of working substance
D.  None of these

PHYSICS HSSC-I
Time allowed: 2:35 Hours
Total Marks = 68

Note: Answer any fourteen parts from Section 'B' and any two questions from Section ‘C the separately provided answer book. Use supplementary answer sheet i.e. Sheet-B if required. Write your answers neatly and legibly.

SECTION - B (Marks 42)

Q. 2 Attempt any FOURTEEN parts. The answer to each part should not exceed 3 to 4 lines. (14 x 3 = 42)

• Why do we find it useful to have two units for the amount of substance, the kilogram and the mole?
• Show that the famous "Einstein equation" E = mc²  is dimensionally correct.
• Find the projection of vector  = 2ȋ— 8ĵ+ Ќ in the direction of the vector = 3— 4ĵ — 12Ќ.
• Show that the sum and difference of two perpendicular vectors of equal lengths are also perpendicular and of the same length. A 1500 kg car has its velocity reduced from
  20ms^-1  to 15ms^-1  in 3.0 seC. How large was the average retarding force?
• Can the velocity of an object reverse the direction when acceleration is constant?
• What is meant by Projectile motion?
• Human metabolism provides an example of law of conservation of energy. Explain on the basis of the 1st law of thermodynamics.
• How does Diesel engine work?
• A thermos flask containing milk as a system is shaken rapidly. Does the temperature of milk rise?
• Why does a diver change his body positions before and after diving in the pool?
• An oil film spreading over a wet footpath shows colors. Explain how it happens.
• A disc and a hoop start moving down from the top of an inclined plane at the same time.
• Which one will be moving faster .on reaching the bottom?
• A boy uses a catapult to throw a stone which accidentally smashes a greenhouse window. List the possible energy changes.
• What happens to the period of a simple pendulum if its length is doubled? What happens if the suspended mass is doubled?
• Why would it be advantageous to use blue light with a compound microscope?
• In "Newton's rings" at the point of contact of the lens' and the glass plate, the spot is dark. Why?
• How are beats useful in tuning musical instruments?
• How should a sound source move with respect to an observer so that the frequency of its sound does not change?

SECTION - C (Marks - 26)

Note: Attempt any TWO questions. All questions carry equal marks.(2 x 13 = 26)

Q. 3 A.Define Torque. Explain the idea of torque due to a force F acting on a rigid body. Discuss two of its special cases. (8)
B. A load of 10.0 N is suspended from a clothes line. This distorts the line so that it makes an angle of 15° with the horizontal at each end. Find the tension in the clothes line. (05)

Q.4 A.Explain Young's double slit interference experiment and show that the bright and dark fringes are of equal width and are equally spaced. (09)
B. Estimate the average speed of nitrogen molecules in air under standard conditions of pressure and temperature (K = 1.38x10^-23  JK^-1 ) (04)

Q.5 A.Write five postulates of "Kinetic Molecular theory". Also prove that pressure exerted by the gas is directly proportional to the average translational kinetic energy of the gas molecules.  (08)
B. A church organ consists of pipes, each open at one end, of different lengths.
The minimum length is 30 mm and the longest is 4m. Calculate the frequency range of the fundamental notes. (Speed of sound = 340ms^-1 )   (05)