AFMC 1999 Physics

Total Questions:50 Total Time: 75 Min

Remaining:

 

Questions 1 of 50

Question:A body is vibrating in simple harmonic motion with an amplitude of 0.06 m and frequency of 15 Hz. The maximum velocity and acceleration of the body is :

Answers Choices:

9.80 m/s and 9.03 x 10\(^2\) m/s\(^2\)

8.90 m/s and 8.21 x 10\(^2\) m/s\(^2\)

6.82 m/s and 7.62 x 10\(^2\) m/s\(^2\)

5.65 m/s and 5.32 x 10\(^2\) m/s\(^2\)

Questions 2 of 50

Question:Kinetic energy of an electron accelerated in a potential difference of 100 V is :

Answers Choices:

1.6 x 10\(^{ - 34}\)J

1.6 x 10\(^{ - 29}\)J

1.6 x 10\(^{ - 21}\)J

1.6 x 10\(^{ - 17}\)J

Questions 3 of 50

Question:If the equation of motion of standing wave is y = 0.3sin(314t - 1.57x). Then the velocity of standing wave is :

Answers Choices:

400 unit

250 unit

200 unit

150 unit

Questions 4 of 50

Question:On producing the waves of frequency 1000 Hz in a Kundt's tube, the total distance between 6 successive nodes is 85 cm. Speed of sound in the gas filled in the tube is :

Answers Choices:

300 m/s

350 m/s

340 m/s

330 m/s

Questions 5 of 50

Question:A particle executes simple harmonic motion of amplitude A. At what distance from the mean position its kinetic energy is equal to its potential energy ?

Answers Choices:

0.81 A

0.71 A

0.61 A

0.51 A

Questions 6 of 50

Question:Diamagnetic substances are :

Answers Choices:

strongly repelled by magnets

feebly repelled by magnets

feebly attracted by magnets

strongly attracted by magnets

Questions 7 of 50

Question:The study of the effects associated with electric field at rest is known as :

Answers Choices:

electrostatics

electromagnetism

magnetostatics

none of these

Questions 8 of 50

Question:For driving current of 2A for 6 min in a I circuit, 1000J of work is to be done. The emf of the source in the circuit is :

Answers Choices:

1.38 V

1.68 V

2.03 V

3.10 V

Questions 9 of 50

Question:A current carrying wire in the neighbourhood I produces :

Answers Choices:

electric and magnetic fields

magnetic field only

no field

electric field

Questions 10 of 50

Question:A resonance air column of length 20 cm resonates with a tuning fork of frequency 250 Hz. The speed of the air is :

Answers Choices:

75 m/s

150 m/s

200 m/s

300 m/s

Questions 11 of 50

Question:An iron rod of length 2m and cross-sectional area of 50 mm2 is stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young's modulus of iron rod is :

Answers Choices:

19.6 x 10\(^{20}\) N/m\(^2\)

19.6 x 10\(^{18}\) N/m\(^2\)

19.6 x 10\(^{10}\) N/m\(^2\)

19.6 x 10\(^{15}\) N/m\(^2\)

Questions 12 of 50

Question:Two parallel wires in free space are 10 cm apart and each carries a current of 10 A in the same direction. The force exerted by one wire on other per metre of length of the wire is:

Answers Choices:

2 x 10\(^{ - 6}\)N

2 x 10\(^{ - 4}\)N

2 x 10\(^{ - 3}\)N

2 x 10\(^{ - 2}\)N

Questions 13 of 50

Question:A wire has resistance of 3.1 Q at 30\(^\circ \)C and resistance 4.5 Q at 100\(^\circ \)C. The temperature coefficient of resistance of the wire is:

Answers Choices:

0.0012\(^\circ \) C\(^{ - 1}\)

0.0024\(^\circ \) C\(^{ - 1}\)

0.0032\(^\circ \) C\(^{ - 1}\)

0.0064\(^\circ \) C\(^{ - 1}\)

Questions 14 of 50

Question:If the current through 3\(\Omega \) resistor is 0.8 A, then potential drop through 4\(\Omega \) resistor is :

Answers Choices:

1.2 V

2.6 V

4.8 V

9.6 V

Questions 15 of 50

Question:The direction of the null points is on the equatorial line of a bar magnet, when the north pole of the magnet is pointing to :

Answers Choices:

West

East

South

North

Questions 16 of 50

Question:Two batteries of emf 4V and 8V having the internal resistance of 1\(\Omega \) and 2\(\Omega \) respectively are connected in circuit with a resistance of 9fi as shown in a figure. The current and potential difference between the points P and Q are :

Answers Choices:

\(\frac{1}{{12}}\)A and 12V

\(\frac{1}{9}\) A and 9V

\(\frac{1}{6}\) A and 4V

\(\frac{1}{3}\) A and 3V

Questions 17 of 50

Question:The dimensions of gravitational constant G are :

Answers Choices:

\(\left[ {{\rm{M}}{{\rm{L}}^{{\rm{ -3}}}}{{\rm{T}}^{{\rm{ - 2}}}}} \right]\)

\(\left[ {{{\rm{M}}^{{\rm{ - 1}}}}{{\rm{L}}^{\rm{2}}}{{\rm{T}}^{{\rm{ - 2}}}}} \right]\)

\(\left[ {{\rm{M}}{{\rm{L}}^{{\rm{ - 2}}}}{{\rm{T}}^{\rm{2}}}} \right]\)

\([{M^{ - 1}}{L^3}{T^{ - 2}}]\)

Questions 18 of 50

Question:A 30 g bullet initially travelling at 120 m/s penetrates 12 cm into wooden block. The average resistance exerted by the wooden block is:

Answers Choices:

1800 N

2000 N

2200 N

2850 N

Questions 19 of 50

Question:A bar magnet of magnetic moment 200 A-m\(^2\) is suspended in a magnetic field of intensity 0.25 N/Am the couple required to deflect it through 30\(^0\) is :

Answers Choices:

15 N-m

20 N-m

25 N-m

50 N-m

Questions 20 of 50

Question:Two magnets each of magnetic moment M are placed so as to form a cross at right angles to each other. The magnetic moment of the system will be :

Answers Choices:

M

0.5M

\(\sqrt 2 \)M

2M

Questions 21 of 50

Question:Plate current will be maximum when :

Answers Choices:

both the grid and anode are negative

both the grid and anode are positive

grid is positive and anode is negative

grid is negative and anode is positive

Questions 22 of 50

Question:Sodium has body centered packing. Distance between two nearest atoms is 3.7\(\mathop A\limits^{\,\,\,0} \) . The lattice parameter is :

Answers Choices:

4.9\(\mathop A\limits^{\,\,\,0} \)

4.3\(\mathop A\limits^{\,\,\,0} \)

3.8\(\mathop A\limits^{\,\,\,0} \)

3.4 \(\mathop A\limits^{\,\,\,0} \)

Questions 23 of 50

Question:A long hollow copper pipe carries a current, then magnetic field produced is :

Answers Choices:

both inside and outside the pipe

neither inside nor outside the pipe

outside the pipe only

inside the pipe only

Questions 24 of 50

Question:Which of the following are not the transverse waves ?

Answers Choices:

Sound waves

Visible light waves

X-rays

y-rays

Questions 25 of 50

Question:The displacement x of a particle moving along a straight line at time t is given by \(x = {a_0} + {a_1}t + {a_2}{t^2}\). The acceleration of the particle is:

Answers Choices:

4a\(_2\)

2a\(_2\)

2a\(_1\)

a\(_2\)

Questions 26 of 50

Question:A bomb is dropped from an aeroplane moving horizontally at constant speed. If air resistance is taken into consideration, then the bomb :

Answers Choices:

falls on earth exactly below the aeroplane

falls on the earth exactly behind the aeroplane

falls on the earths ahead of the aeroplane

flies with the aeroplane

Questions 27 of 50

Question:In a p-type semiconductor germanium is doped with :

Answers Choices:

aluminium

boron

gallium

all of these

Questions 28 of 50

Question:In a triode valve, the current in the plate circuit is controlled by :

Answers Choices:

ammeter

grid

cathode

anode

Questions 29 of 50

Question:When a bus suddenly takes a turn, the passengers are thrown outwards because of:

Answers Choices:

speed of motion

inertia of motion

acceleration of motion

none of the above

Questions 30 of 50

Question:The logic behind NOR gate is that which gives

Answers Choices:

high output when both inputs are high

low output when both inputs are low

high output when both inputs are low

none of the above

Questions 31 of 50

Question:Which of the following statements is not correct ?

Answers Choices:

Infra-red photons have more energy than photons of visible light

Infra-red rays are invisible but can cast shadows like visible light

Photographic plates are sensitive to ultraviolet rays

Photographic plates are sensitive to infrared rays

Questions 32 of 50

Question:In which sequence the radioactive radiations are emitted in the following nuclear reaction ? \(_Z{X^A}{ \to _{Z + 1}}{Y^A}{ \to _{Z - 1}}{K^{A - 4}}{ \to _{Z - 1}}{K^{A - 4}}\)

Answers Choices:

\(\gamma ,\alpha \) and \(\beta \)

\(\alpha \), \(\beta \) and \(\gamma \)

\(\beta \), \(\alpha \) and \(\gamma \)

\(\beta \), \(\gamma \) and \(\alpha \)

Questions 33 of 50

Question:If red light and violet light rays are of focal lengths \({f_R}\) and \({f_v}\), then which one of the following is true ?

Answers Choices:

\({\lambda _R} \le {\lambda _v}\)

\({\mu _R} > {\mu _v}\)

\({\lambda _R} = {\lambda _v}\)

\({\mu _R} < {\mu _v}\)

Questions 34 of 50

Question:The large scale destruction, that would be caused due to the use of nuclear weapons is known as :

Answers Choices:

neutron reproduction factor

nuclear holocaust

thermonuclear reaction

none of the above

Questions 35 of 50

Question:If in Ramsden's eyepiece, the field lenses have focal lengths \({f_1}\) and \({f_2}\) respectively and separated by a distance d then :

Answers Choices:

\({f_1}\) = \(3{f_2}\) and d = \({f_1}\) + \({f_2}\)

\({f_1}\) = \({f_2}\) and d= \(\frac{2}{3}{f_1}\)

\({f_1}\) = \(\frac{2}{3}\) and d = \(\frac{2}{3}{f_1}\)

\({f_1}\) = \({f_2}\) and d = \({f_1}\) + \({f_2}\)

Questions 36 of 50

Question:Huygen's wave theory of light could not explain :

Answers Choices:

photoelectric effect

polarization

diffraction

interference

Questions 37 of 50

Question:The rain drops are spherical in shape due to :

Answers Choices:

residual pressure

thrust on drop

surface tension

viscosity

Questions 38 of 50

Question:The work done in pulling up a block of wood weighing 2 kN for a length of 10m on a smooth plane inclined at an angle of 15 \(^0\) with the horizontal is :

Answers Choices:

9.82 k J

8.91 k J

5.17 k J

4.36 k J

Questions 39 of 50

Question:The thermions are :

Answers Choices:

positrons

photons

electrons

protons

Questions 40 of 50

Question:The internal resistance of cell of emf 2V is 0.1 \(\Omega \). It is connected to a resistance of 3.9ft. The voltage across the cell is:

Answers Choices:

2.71V

1.95 V

1.68 V

0.52 V

Questions 41 of 50

Question:The earth of mass 6 x 10\(^{{\rm{24}}}\) kg revolves around the sum with an angular velocity of 2 x 10\(^{ - 7}\) rad/s. In a circular orbit of radius 1.5 x 10\(^8\) km, the force exerted by the sun, on the earth is :

Answers Choices:

27 x 10\(^{39}\) N

36 x 10\(^{21}\) N

18 x 10\(^{25}\) N

6 x 10\(^{19}\) N

Questions 42 of 50

Question:A stone is thrown with an initial speed of 4.9 m/s from a bridge in vertically upward direction. It falls down in water after 2 s. The height of the bridge is :

Answers Choices:

24.7 m

19.8 m

9.8 m

4.9 m

Questions 43 of 50

Question:A ball of mass 150g moving with an acceleration 20 m/s\(^2\) is hit by a force, which acts, on it for 0.1 s. The impulsive force is :

Answers Choices:

1.2 Ns

0.3 Ns

0.1 Ns

0.5 Ns

Questions 44 of 50

Question:If the heat of 110 J is added to a gaseous system, whose internal energy is 40 J, then the amount of external work done is:

Answers Choices:

80 J

70 J

115 J

140 J

Questions 45 of 50

Question:The substance in which the magnetic moment of a single atom is not zero, is called as :

Answers Choices:

ferrimagnetism

paramagnetism

ferromagnetism

diamagnetism

Questions 46 of 50

Question:The luminous efficiency of a lamp is 4 lumen/W and its luminous intensity is 30 cd. The power of lamp is :

Answers Choices:

60 W

78 W

94 W

136 W

Questions 47 of 50

Question:The work function of aluminium is 4.2 eV. If two photons each of energy 3.5 eV strike an electron of aluminium, then emission of electron :

Answers Choices:

depended upon the density of the surface

data is incomplete

is not possible

is possible

Questions 48 of 50

Question:Two vectors \(\vec A\) and \(\vec B\) are such that A + B = C and \({A^2} + {\rm{ }}{B^2} = {{\rm{C}}^{\rm{2}}}\). If 6 is the angle between \(\vec A\) and \(\vec B\)then the correct statement is :

Answers Choices:

\(\theta = \pi \)

\(\theta = \frac{{2\pi }}{3}\)

\(\theta = 0\)

\(\theta = \frac{\pi }{2}\)

Questions 49 of 50

Question:A rough vertical board has an acceleration a along the horizontal so that a block of mass M pressing against it does not fall. The coefficient of friction between block and the board is :

Answers Choices:

\( > \frac{a}{g}\)

\( < \frac{g}{a}\)

\( = \frac{a}{g}\)

\( > \frac{a}{g}\)

Questions 50 of 50

Question:An aeroplane is moving with a horizontal velocity u at a height h. The velocity of packet dropped from it on the earth's surface will be :

Answers Choices:

\(\sqrt {{u^2} - 2gh} \)

\({2gh}\)

\(\sqrt {2gh} \)

\(\sqrt {{u^2} + 2gh} \)