12583 + Mcqs in Physics Page 16 McqOptions

751.	The surface tension of a liquid at its boiling point [MP PMT 1980]
A.	Becomes zero
B.	Becomes infinity
C.	is equal to the value at room temperature
D.	is half to the value at the room temperature
Answer» B. Becomes infinity

Discussion

752.	A body is executing S.H.M. When its displacement from the mean position is 4 cm and 5 cm, the corresponding velocity of the body is 10 cm/sec and 8 cm/sec. Then the time period of the body is [CPMT 1991; MP PET 1995]
A.	\[2\pi \,sec\]
B.	\[\pi /2\]sec
C.	\[\pi \,sec\]
D.	\[3\pi /2\,sec\]
Answer» D. \[3\pi /2\,sec\]

Discussion

753.	The particle executing simple harmonic motion has a kinetic energy\[{{K}_{0}}{{\cos }^{2}}\omega t\]. The maximum values of the potential energy and the total energy are respectively
A.	\[{{K}_{0}}/2\,and\,{{K}_{0}}\]
B.	\[{{K}_{0}}\,and\,2{{K}_{0}}\]
C.	\[{{K}_{0}}\,and\,{{K}_{0}}\]
D.	\[0\,and\,2{{K}_{0}}\]
Answer» D. \[0\,and\,2{{K}_{0}}\]

Discussion

754.	Assertion : A narrow pulse of light is sent through a medium. The pulse will retain its shape as it travels through the medium. Reason : A narrow pulse is made of harmonic waves with a large range of wavelengths.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

755.	Assertion : Newton?s rings are formed in the reflected system. When the space between the lens and the glass plate is filled with a liquid of refractive index greater than that of glass, the central spot of the pattern is dark. Reason : The reflection is Newton?s ring cases will be from a denser to a rarer medium and the two interfering rays are reflected under similar conditions. [AIIMS 1998]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

756.	Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other. Reason : The fringe width is inversely proportional to the distance between the two slits.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

757.	A hot body, obeying Newton's law of cooling is cooling down from its peak value \[89{}^\circ C\] to an ambient temperature of \[39{}^\circ C\]. It takes 5 minutes in cooling down from \[89{}^\circ C\] to \[49{}^\circ C\]. How much time will it take to cool down from \[62{}^\circ C to 32{}^\circ C\](Given In 2 = 9.693, In 5 = 1.699)
A.	3.75 minutes
B.	8.6 minutes
C.	9.6 minutes
D.	6.5 minutes
Answer» C. 9.6 minutes

Discussion

758.	The slope of plate characteristic of a vacuum tube diode for certain operating point on the curve is \[{{10}^{-3}}\frac{mA}{V}\]. The plate resistance of the diode and its nature respectively [MP PMT 1990]
A.	100 kilo-ohms static
B.	1000 kilo-ohms static
C.	1000 kilo-ohms dynamic
D.	100 kilo-ohms dynamic
Answer» C. 1000 kilo-ohms dynamic

Discussion

759.	The refractive index of water is 4 / 3 and that of glass is 5/3. What will be the critical angle for the ray of light entering water from the glass [RPMT 1996]
A.	\[{{\sin }^{-1}}\frac{4}{5}\]
B.	\[{{\sin }^{-1}}\frac{5}{4}\]
C.	\[{{\sin }^{-1}}\]\[\frac{1}{2}\]
D.	\[{{\sin }^{-1}}\frac{2}{1}\]
Answer» B. \[{{\sin }^{-1}}\frac{5}{4}\]

Discussion

760.	The velocity of light in a medium is half its velocity in air. If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected, is [Roorkee 1999]
A.	\[{{15}^{o}}\]
B.	\[{{30}^{o}}\]
C.	\[{{45}^{o}}\]
D.	\[{{60}^{o}}\]
Answer» C. \[{{45}^{o}}\]

Discussion

761.	Assertion : Cyclotron does not accelerate electron. Reason : Mass of the electron is very small. [AIIMS 2000]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

762.	In figure, a block having a mass of 5 kg is released from rest, where the spring acting on the body are horizontal and have a tension of 50 N. The force constant of each spring is, \[k=500\text{ }N/m\]. The velocity of the block after it has descended by 0.3m.
A.	0
B.	I m/s
C.	2 m/s
D.	none
Answer» B. I m/s

Discussion

763.	An electron moving in a circular orbit of radius r makes n rotation per second. The magnetic field produced at the centre has a magnitude of [KCET 2001; UPSEAT 2001, 02]
A.	\[\frac{{{\mu }_{0}}ne}{2r}\]
B.	\[\frac{{{\mu }_{0}}{{n}^{2}}e}{2r}\]
C.	\[\frac{{{\mu }_{0}}ne}{2\pi r}\]
D.	Zero
Answer» B. \[\frac{{{\mu }_{0}}{{n}^{2}}e}{2r}\]

Discussion

764.	Assertion : Chock coil is preferred over a resistor to adjust current in an ac circuit. Reason : Power factor for inductance is zero.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

765.	The cathode rays have particle nature because of the fact that [CPMT 1986; MNR 1986]
A.	They can propagate in vacuum
B.	They are deflected by electric and magnetic fields
C.	They produced fluorescence
D.	They cast shadows
Answer» C. They produced fluorescence

Discussion

766.	Assertion : A body may be accelerated even when it is moving uniformly. Reason : When direction of motion of the body is changing then body may have acceleration.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» F.

Discussion

767.	At the height 80 m, an aeroplane is moving with 150 m/s. A bomb is dropped from it so as to hit a target. At what distance from the target should the bomb be dropped (given \[g=\text{ }10m/{{s}^{2}}\])
A.	605.3 m
B.	600 m
C.	80 m
D.	230 m
Answer» B. 600 m

Discussion

768.	A gaseous mixture contains equal number of hydrogen and nitrogen molecules. Specific heat measurements on this mixture at temperatures below 100 K would indicate that the value of \[\gamma \] (ratio of specific heats) for this mixture is
A.	44230
B.	44259
C.	44260
D.	44323
Answer» D. 44323

Discussion

769.	The relation between the gas pressure P and average kinetic energy per unit volume E is
A.	\[P=\frac{1}{2}E\]
B.	P = E
C.	\[P=\frac{3}{2}E\]
D.	\[P=\frac{2}{3}E\]
Answer» E.

Discussion

770.	Two identical spring of constant K are connected in series and parallel as shown in figure. A mass m is suspended from them. The ratio of their frequencies of vertical oscillations will be [MP PET 1993; BHU 1997]
A.	2 : 1
B.	1 : 1
C.	1 : 2
D.	4 : 1
Answer» D. 4 : 1

Discussion

771.	A spring is stretched by 0.20 m, when a mass of 0.50 kg is suspended. When a mass of 0.25 kg is suspended, then its period of oscillation will be \[(g=10m/{{s}^{2}})\]
A.	0.328 sec
B.	0.628 sec
C.	0.137 sec
D.	1.00 sec
Answer» C. 0.137 sec

Discussion

772.	A mass m is suspended from the two coupled springs connected in series. The force constant for springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. The time period of the suspended mass will be [CBSE PMT 1990; Pb. PET 2002]
A.	\[T=2\pi \sqrt{\left( \frac{m}{{{K}_{1}}+{{K}_{2}}} \right)}\]
B.	\[T=2\pi \sqrt{\left( \frac{m}{{{K}_{1}}+{{K}_{2}}} \right)}\]
C.	\[T=2\pi \sqrt{\left( \frac{m({{K}_{1}}+{{K}_{2}})}{{{K}_{1}}{{K}_{2}}} \right)}\]
D.	\[T=2\pi \sqrt{\left( \frac{m{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}} \right)}\]
Answer» D. \[T=2\pi \sqrt{\left( \frac{m{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}} \right)}\]

Discussion

773.	Dimensionally wavelength is equivalent to
A.	\[\frac{E\sqrt{LC}}{B}\]
B.	\[\frac{E}{B\sqrt{LC}}\]
C.	\[\frac{B\sqrt{LC}}{E}\]
D.	\[\frac{B}{E\sqrt{LC}}\]
Answer» B. \[\frac{E}{B\sqrt{LC}}\]

Discussion

774.	Assertion : To float, a body must displace liquid whose weight is greater than the actual weight of the body. Reason : The body will experiences no net downward force, in the case of floating.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

775.	Assertion : Soft iron is used as a core of transformer. Reason : Area of hysteresis is loop for soft iron is small.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

776.	A bead of mass m is sliding down the fixed inclined rod without friction. It is connected to a point P on the horizontal surface with a light spring of spring constant k. The bead is initially released from rest and the spring is initially unstressed and vertical. The bead just stops at the bottom of the inclined rod. Find the angle which the inclined rod makes with horizontal.
A.	\[{{\cot }^{-1}}\left( 1+\sqrt{\frac{2mg}{kh}} \right)\]
B.	\[ta{{n}^{-1}}\left( 1+\sqrt{\frac{2mg}{kh}} \right)\]
C.	\[{{\cot }^{-1}}\left( 1+\sqrt{\frac{mg}{kh}} \right)\]
D.	\[ta{{n}^{-1}}\left( 1+\sqrt{\frac{mg}{kh}} \right)\]
Answer» B. \[ta{{n}^{-1}}\left( 1+\sqrt{\frac{2mg}{kh}} \right)\]

Discussion

777.	An X-ray tube operates on 30 kV. What is the minimum wavelength emitted \[(h=6.6\times {{10}^{-34}}\]Js, \[e=1.6\times {{10}^{-19}}\]Coulomb, \[c=3\times {{10}^{8}}\]ms?1) [MP PMT 1995; DPMT 2001, 03]
A.	0.133 Å
B.	0.4 Å
C.	1.2 Å
D.	6.6 Å
Answer» C. 1.2 Å

Discussion

778.	If \[{{V}_{H}},\,\,{{V}_{N}}\] and \[{{V}_{O}}\] denote the root-mean square velocities of molecules of hydrogen, nitrogen and oxygen respectively at a given temperature, then
A.	\[{{V}_{N}}>{{V}_{O}}>{{V}_{H}}\]
B.	\[{{V}_{H}}>{{V}_{N}}>{{V}_{O}}\]
C.	\[{{V}_{O}}={{V}_{N}}={{V}_{H}}\]
D.	\[{{V}_{O}}>{{V}_{H}}>{{V}_{N}}\]
Answer» C. \[{{V}_{O}}={{V}_{N}}={{V}_{H}}\]

Discussion

779.	Assertion : In a movie, ordinarily 24 frames are projected per second from one end to the other of the complete film. Reason : The image formed on retina of eye is sustained upto 1/10 second after the removal of stimulus. [AIIMS 2001]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

780.	Assertion : The air bubble shines in water. Reason : Air bubble in water shines due to refraction of light [AIIMS 2002]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

781.	The amplification factor of a triode is 50. If the grid potential is decreased by 0.20 V, what increase in plate potential will keep the plate current unchanged [RPMT 1999]
A.	5 V
B.	10 V
C.	0.2 V
D.	50 V
Answer» C. 0.2 V

Discussion

782.	Assertion : Blue colour of sky appears due to scattering of blue colour. Reason : Blue colour has shortest wave length in visible spectrum. [AIIMS 2001]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

783.	A position dependent force \[F=7-2x+3{{x}^{2}}\,newton\] acts on a small body of mass 2 kg and displaces it from \[x=0\] to \[x=5\,m\]. The work done in joules is [CBSE PMT 1994]
A.	70
B.	270
C.	35
D.	135
Answer» E.

Discussion

784.	On centigrade scale the temperature of a body increases by 30 degrees. The increase in temperature on Fahrenheit scale is [UPSEAT 2005]
A.	50°
B.	40°
C.	30°
D.	54°
Answer» E.

Discussion

785.	Assertion : Mass is a measure of inertia of the body in linear motion. Reason : Greater the mass, greater is the force required to change its state of rest or of uniform motion.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

786.	Glass has refractive index m with respect to air and the critical angle for a ray of light going from glass to air is q. If a ray of light is incident from air on the glass with angle of incidence q, the corresponding angle of refraction is [MP PMT 2004]
A.	\[{{\sin }^{-1}}\left( \frac{1}{\sqrt{\mu }} \right)\]
B.	\[{{90}^{o}}\]
C.	\[{{\sin }^{-1}}\left( \frac{1}{{{\mu }^{2}}} \right)\]
D.	\[{{\sin }^{-1}}\left( \frac{1}{\mu } \right)\]
Answer» D. \[{{\sin }^{-1}}\left( \frac{1}{\mu } \right)\]

Discussion

787.	Material A has critical angle \[{{i}_{A}},\] and material B has critical angle \[{{i}_{B}}({{i}_{B}}>{{i}_{A}}).\] Then which of the following is true (i) Light can be totally internally reflected when it passes from B to A (ii) Light can be totally internally reflected when it passes from A to B (iii) Critical angle for total internal reflection is \[{{i}_{B}}-{{i}_{A}}\] (iv) Critical angle between A and B is \[{{\sin }^{-1}}\left( \frac{\sin {{i}_{A}}}{\sin {{i}_{B}}} \right)\] [UPSEAT 2004]
A.	(i) and (iii)
B.	(i) and (iv)
C.	(ii) and (iii)
D.	(ii) and (iv)
Answer» E.

Discussion

788.	An element A decays into an element C by a two-step process\[:\text{ }A\to B+He_{2}^{4}\] and \[B\to C+2e_{0}^{-1}\]Then
A.	A and C are isotopes
B.	A and C are isobars
C.	B and C are isotopes
D.	A and B are isobars
Answer» B. A and C are isobars

Discussion

789.	A fish is a little away below the surface of a lake. If the critical angle is 49°, then the fish could see things above the water surface within an angular range of \[{{\theta }^{o}}\] where [MP PMT 1986]
A.	\[\theta ={{49}^{o}}\]
B.	\[\theta ={{90}^{o}}\]
C.	\[\theta ={{98}^{o}}\]
D.	\[\theta =24\frac{{{1}^{o}}}{2}\]
Answer» D. \[\theta =24\frac{{{1}^{o}}}{2}\]

Discussion

790.	A ray of light is incident at an angle i from denser to rare medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection and the angle of refraction are respectively r and r' , then the critical angle will be [IIT-JEE 1983; MP PET 1995; CBSE PMT 1996; MP PMT 1985, 99; Pb. PET 2002]
A.	\[{{\sin }^{-1}}(\sin \,r)\]
B.	\[{{\sin }^{-1}}\,(\tan r')\]
C.	\[{{\sin }^{-1}}\,(\tan i)\]
D.	\[{{\tan }^{-1}}(\sin i)\]
Answer» D. \[{{\tan }^{-1}}(\sin i)\]

Discussion

791.	If the critical angle for total internal reflection from a medium to vacuum is \[30{}^\circ \], the velocity of light in the medium is [CPMT 1972; MH CET 2000; KCET 2000; BCECE 2003; RPMT 2003]
A.	\[3\times {{10}^{8}}\] m/s
B.	\[1.5\times {{10}^{8}}\] m/s
C.	\[6\times {{10}^{8}}\] m/s
D.	\[\sqrt{3}\times {{10}^{8}}\]m/s
Answer» C. \[6\times {{10}^{8}}\] m/s

Discussion

792.	Assertion : When PN-junction is forward biased then motion of charge carriers at junction is due to diffusion. In reverse biasing. The cause of motion of charge is drifting. Reason : In the following circuit emitter is reverse biased and collector is forward biased.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

793.	Assertion : 29 is the equivalent decimal number of binary number 11101. Reason : (11101)2 = (1 ´ 24 + 1 ´ 23 + 1 ´ 22 + 0 ´ 21 + 1 ´ 20 )10 = (16 + 8 + 4 + 0 + 1)10 = (29)10
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

794.	Assertion : De-morgan's theorem \[\overline{A+B}=\bar{A}\cdot \bar{B}\] may be explained by the following circuit Reason : In the following circuit, for output inputs ABC are 101
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

795.	The length of a metallic rod is 5 m at \[0{}^\circ C\]and becomes 5.01 m, on heating up to\[100{}^\circ C\]. The linear expansion of the metal will be
A.	\[2.33\times {{10}^{-5}}/{}^\circ C\]
B.	\[6.0\times {{10}^{-5}}/{}^\circ C\]
C.	\[4.0\times {{10}^{-5}}/{}^\circ C\]
D.	\[2.0\times {{10}^{-5}}/{}^\circ C\]
Answer» E.

Discussion

796.	In the situation shown in the figure, the system is in equilibrium. All the strings, spring and pulley are light. Just after cutting the string AB,
A.	the tension in the string GH is 6 g
B.	the tension in the string GH is zero
C.	the tension in string GH is \[\frac{21}{4}g\]
D.	the 2 kg block remains in equilibrium
Answer» D. the 2 kg block remains in equilibrium

Discussion

797.	In extrinsic P and N-type, semiconductor materials, the ratio of the impurity atoms to the pure semiconductor atoms is about [MP PET 2003]
A.	1
B.	\[{{10}^{-1}}\]
C.	\[{{10}^{-4}}\]
D.	\[{{10}^{-7}}\]
Answer» E.

Discussion

798.	In intrinsic semiconductor at room temperature, number of electrons and holes are [EAMCET (Engg.) 1995; JIPMER 2001, 02]
A.	Equal
B.	Zero
C.	Unequal
D.	Infinite
Answer» B. Zero

Discussion

799.	The number of turns of primary and secondary coils of a transformer are 5 and 10 respectively and the mutual inductance of the transformer is 25 henry. Now the number of turns in the primary and secondary of the transformer are made 10 and 5 respectively. The mutual inductance of the transformer in henry will be [MP PET 1995]
A.	6.25
B.	12.5
C.	25
D.	50
Answer» D. 50

Discussion

800.	A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of the motion of the ball is [Kerala PET 2005]
A.	1 : 2 : 3
B.	1 : 4 : 9
C.	1 : 3 : 5
D.	1 : 5 : 3
Answer» D. 1 : 5 : 3

Discussion

Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

The surface tension of a liquid at its boiling point [MP PMT 1980]

A body is executing S.H.M. When its displacement from the mean position is 4 cm and 5 cm, the corresponding velocity of the body is 10 cm/sec and 8 cm/sec. Then the time period of the body is [CPMT 1991; MP PET 1995]

The particle executing simple harmonic motion has a kinetic energy\[{{K}_{0}}{{\cos }^{2}}\omega t\]. The maximum values of the potential energy and the total energy are respectively

Assertion : A narrow pulse of light is sent through a medium. The pulse will retain its shape as it travels through the medium. Reason : A narrow pulse is made of harmonic waves with a large range of wavelengths.

Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other. Reason : The fringe width is inversely proportional to the distance between the two slits.

The slope of plate characteristic of a vacuum tube diode for certain operating point on the curve is \[{{10}^{-3}}\frac{mA}{V}\]. The plate resistance of the diode and its nature respectively [MP PMT 1990]

The refractive index of water is 4 / 3 and that of glass is 5/3. What will be the critical angle for the ray of light entering water from the glass [RPMT 1996]

The velocity of light in a medium is half its velocity in air. If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected, is [Roorkee 1999]

Assertion : Cyclotron does not accelerate electron. Reason : Mass of the electron is very small. [AIIMS 2000]

In figure, a block having a mass of 5 kg is released from rest, where the spring acting on the body are horizontal and have a tension of 50 N. The force constant of each spring is, \[k=500\text{ }N/m\]. The velocity of the block after it has descended by 0.3m.

An electron moving in a circular orbit of radius r makes n rotation per second. The magnetic field produced at the centre has a magnitude of [KCET 2001; UPSEAT 2001, 02]

Assertion : Chock coil is preferred over a resistor to adjust current in an ac circuit. Reason : Power factor for inductance is zero.

The cathode rays have particle nature because of the fact that [CPMT 1986; MNR 1986]

Assertion : A body may be accelerated even when it is moving uniformly. Reason : When direction of motion of the body is changing then body may have acceleration.

At the height 80 m, an aeroplane is moving with 150 m/s. A bomb is dropped from it so as to hit a target. At what distance from the target should the bomb be dropped (given \[g=\text{ }10m/{{s}^{2}}\])

A gaseous mixture contains equal number of hydrogen and nitrogen molecules. Specific heat measurements on this mixture at temperatures below 100 K would indicate that the value of \[\gamma \] (ratio of specific heats) for this mixture is

The relation between the gas pressure P and average kinetic energy per unit volume E is

Two identical spring of constant K are connected in series and parallel as shown in figure. A mass m is suspended from them. The ratio of their frequencies of vertical oscillations will be [MP PET 1993; BHU 1997]

A spring is stretched by 0.20 m, when a mass of 0.50 kg is suspended. When a mass of 0.25 kg is suspended, then its period of oscillation will be \[(g=10m/{{s}^{2}})\]

A mass m is suspended from the two coupled springs connected in series. The force constant for springs are \[{{K}_{1}}\] and \[{{K}_{2}}\]. The time period of the suspended mass will be [CBSE PMT 1990; Pb. PET 2002]

Dimensionally wavelength is equivalent to

Assertion : To float, a body must displace liquid whose weight is greater than the actual weight of the body. Reason : The body will experiences no net downward force, in the case of floating.

Assertion : Soft iron is used as a core of transformer. Reason : Area of hysteresis is loop for soft iron is small.

An X-ray tube operates on 30 kV. What is the minimum wavelength emitted \[(h=6.6\times {{10}^{-34}}\]Js, \[e=1.6\times {{10}^{-19}}\]Coulomb, \[c=3\times {{10}^{8}}\]ms?1) [MP PMT 1995; DPMT 2001, 03]

If \[{{V}_{H}},\,\,{{V}_{N}}\] and \[{{V}_{O}}\] denote the root-mean square velocities of molecules of hydrogen, nitrogen and oxygen respectively at a given temperature, then

Assertion : In a movie, ordinarily 24 frames are projected per second from one end to the other of the complete film. Reason : The image formed on retina of eye is sustained upto 1/10 second after the removal of stimulus. [AIIMS 2001]

Assertion : The air bubble shines in water. Reason : Air bubble in water shines due to refraction of light [AIIMS 2002]

The amplification factor of a triode is 50. If the grid potential is decreased by 0.20 V, what increase in plate potential will keep the plate current unchanged [RPMT 1999]

Assertion : Blue colour of sky appears due to scattering of blue colour. Reason : Blue colour has shortest wave length in visible spectrum. [AIIMS 2001]

A position dependent force \[F=7-2x+3{{x}^{2}}\,newton\] acts on a small body of mass 2 kg and displaces it from \[x=0\] to \[x=5\,m\]. The work done in joules is [CBSE PMT 1994]

On centigrade scale the temperature of a body increases by 30 degrees. The increase in temperature on Fahrenheit scale is [UPSEAT 2005]

Assertion : Mass is a measure of inertia of the body in linear motion. Reason : Greater the mass, greater is the force required to change its state of rest or of uniform motion.

Glass has refractive index m with respect to air and the critical angle for a ray of light going from glass to air is q. If a ray of light is incident from air on the glass with angle of incidence q, the corresponding angle of refraction is [MP PMT 2004]

An element A decays into an element C by a two-step process\[:\text{ }A\to B+He_{2}^{4}\] and \[B\to C+2e_{0}^{-1}\]Then

A fish is a little away below the surface of a lake. If the critical angle is 49°, then the fish could see things above the water surface within an angular range of \[{{\theta }^{o}}\] where [MP PMT 1986]

If the critical angle for total internal reflection from a medium to vacuum is \[30{}^\circ \], the velocity of light in the medium is [CPMT 1972; MH CET 2000; KCET 2000; BCECE 2003; RPMT 2003]

Assertion : When PN-junction is forward biased then motion of charge carriers at junction is due to diffusion. In reverse biasing. The cause of motion of charge is drifting. Reason : In the following circuit emitter is reverse biased and collector is forward biased.

Assertion : 29 is the equivalent decimal number of binary number 11101. Reason : (11101)2 = (1 ´ 24 + 1 ´ 23 + 1 ´ 22 + 0 ´ 21 + 1 ´ 20 )10 = (16 + 8 + 4 + 0 + 1)10 = (29)10

Assertion : De-morgan's theorem \[\overline{A+B}=\bar{A}\cdot \bar{B}\] may be explained by the following circuit Reason : In the following circuit, for output inputs ABC are 101

The length of a metallic rod is 5 m at \[0{}^\circ C\]and becomes 5.01 m, on heating up to\[100{}^\circ C\]. The linear expansion of the metal will be

In the situation shown in the figure, the system is in equilibrium. All the strings, spring and pulley are light. Just after cutting the string AB,

In extrinsic P and N-type, semiconductor materials, the ratio of the impurity atoms to the pure semiconductor atoms is about [MP PET 2003]

In intrinsic semiconductor at room temperature, number of electrons and holes are [EAMCET (Engg.) 1995; JIPMER 2001, 02]

A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of the motion of the ball is [Kerala PET 2005]