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question_answer1) Which graph correctly presents the variation of acceleration due to gravity with the distance from the centre of the earth (radius of the earth \[={{R}_{E}}\])?
JEE Main Online Paper (Held On 07 May 2012)
A)
done
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B)
done
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C)
done
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D)
done
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question_answer2) A car of mass 1000 kg is moving at a speed of 30m/s. Brakes are applied to bring the car to rest. If the net retarding force is 5000 N, the car comes to stop after travelling dm in t s. Then
JEE Main Online Paper (Held On 07 May 2012)
A)
\[d=150,t=5\]
done
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B)
\[d=120,t=8\]
done
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C)
\[d=180,t=6\]
done
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D)
\[d=90,t=6\]
done
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question_answer3) A perfect gas at \[27{}^\circ C\] is heated at constant pressure so as to double its volume. The final temperature of the gas will be, close to
JEE Main Online Paper (Held On 07 May 2012)
A)
\[327{}^\circ C\]
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B)
\[200{}^\circ C\]
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C)
\[54{}^\circ C\]
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D)
\[300{}^\circ C\]
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question_answer4)
A square hole of side length i is made at a depth of h and a circular hole of radius r is made at adepth of 4h from the surface of water in a water tank kept on a horizontal surface. If \[\ell <<h, r<<h\]and the rate of water flow from the holes is the same, then r is equal to 
JEE Main Online Paper (Held On 07 May 2012)
A)
\[\frac{\ell }{\sqrt{2\pi }}\]
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B)
\[\frac{\ell }{\sqrt{3\pi }}\]
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C)
\[\frac{\ell }{3\pi }\]
done
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D)
\[\frac{\ell }{2\pi }\]
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question_answer5) A structural steel rod has a radius of 10 mm and length of 1.0 m. A 100 kN force stretches it along its length. Young's modulus of structural steel is\[2\times {{10}^{11}}N{{m}^{-2}}.\]The percentage strain is about
JEE Main Online Paper (Held On 07 May 2012)
A)
0.16%
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B)
0.32%
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C)
0.08%
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D)
0.24%
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question_answer6) The heat radiated per unit area in 1 hour by a furnace whose temperature is 3000 K is \[(\sigma =5.7\times {{10}^{-8}}W\,{{m}^{-2}}{{K}^{-4}})\]
JEE Main Online Paper (Held On 07 May 2012)
A)
\[1.7\times {{10}^{10}}J\]
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B)
\[1.1\times {{10}^{12}}J\]
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C)
\[2.8\times {{10}^{8}}J\]
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D)
\[4.6\times {{10}^{6}}J\]
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question_answer7) Broadcasting antennas are generally
JEE Main Online Paper (Held On 07 May 2012)
A)
vertical type
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B)
both vertical and horizontal type
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C)
omni directional type
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D)
horizontal type
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question_answer8) The velocity of certain ions that pass undeflected through crossed electric field E = 7.7 k V/m and magnetic field B = 0.14T is
JEE Main Online Paper (Held On 07 May 2012)
A)
18km/s
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B)
77km/s
done
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C)
55km/s.
done
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D)
1078 km/s
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question_answer9) Following are expressions for four plane simple harmonic waves (i)\[{{y}_{1}}=A\cos 2\pi \left( {{n}_{1}}t+\frac{x}{{{\lambda }_{1}}} \right)\] (ii\[{{y}_{2}}=A\cos 2\pi \left( {{n}_{1}}t+\frac{x}{{{\lambda }_{1}}}+\pi \right)\] (iii)\[{{y}_{3}}=A\cos 2\pi \left( {{n}_{1}}t+\frac{x}{{{\lambda }_{2}}} \right)\] (iv)\[{{y}_{4}}=A\cos 2\pi \left( {{n}_{2}}t-\frac{x}{{{\lambda }_{2}}} \right)\] The pairs of waves which will produce destructive interference and stationary waves respectively in a medium, are
JEE Main Online Paper (Held On 07 May 2012)
A)
(iii, iv), (i, ii)
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B)
(i, iii), (ii, iv)
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C)
(i,iv),(ii,iii)
done
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D)
(i, ii), (iii, iv)
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question_answer10) An engine pumps water continuously through a hose. Water leaves the hose with velocity v and m is mass per unit length of the water jet. If this jet hits a surface and came to rest instantaneously, the force on the surface is
A)
\[m{{v}^{3}}\]
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B)
\[m{{v}^{2}}\]
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C)
\[\frac{1}{2}m{{v}^{2}}\]
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D)
\[\frac{1}{2}m{{v}^{3}}\]
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question_answer11) The electron of a hydrogen atom makes a transition from the \[{{(n+1)}^{th}}\]orbit to the \[{{n}^{th}}\] orbit. For large n the wavelength of the emitted radiation is proportional to
JEE Main Online Paper (Held On 07 May 2012)
A)
n
done
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B)
\[{{n}^{3}}\]
done
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C)
\[{{n}^{4}}\]
done
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D)
\[{{n}^{2}}\]
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question_answer12)
The graph of an object's motion (along the x-axis) is shown in the figure. The instantaneous velocity of the object at points A and B are \[{{v}_{A}}\]and \[{{v}_{B}}\] respectively. Then 
JEE Main Online Paper (Held On 07 May 2012)
A)
\[{{v}_{A}}={{v}_{B}}=0.5m/s\]
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B)
\[{{v}_{A}}=0.5m/s<{{v}_{B}}\]
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C)
\[{{v}_{A}}=0.5m/s>{{v}_{B}}\]
done
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D)
\[{{v}_{A}}={{v}_{B}}=2m/s\]
done
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question_answer13) A circular hole of diameter R is cut from a disc of mass M and radius R, -the circumference of the cut passes through the centre of the disc. The moment of inertia of the remaining portion of the disc about an axis perpendicular to the disc and passing through its centre is
JEE Main Online Paper (Held On 07 May 2012)
A)
\[\left( \frac{15}{32} \right)M{{R}^{2}}\]
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B)
\[\left( \frac{1}{8} \right)M{{R}^{2}}\]
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C)
\[\left( \frac{3}{8} \right)M{{R}^{2}}\]
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D)
\[\left( \frac{13}{32} \right)M{{R}^{2}}\]
done
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question_answer14) In a Young's double slit experiment with light of wavelength\[\lambda ,\] fringe pattern on the screen has fringe width \[\beta .\] When two thin transparent glass(refractive index \[\mu \])plates of thickness \[{{t}_{1}}\] and \[{{t}_{2}}\]\[({{t}_{1}}>{{t}_{2}})\]are placed in the path of the two beams respectively, the fringe pattern will shift by a distance
JEE Main Online Paper (Held On 07 May 2012)
A)
\[\frac{\beta (\mu -1)}{\lambda }\left( \frac{{{t}_{1}}}{{{t}_{2}}} \right)\]
done
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B)
\[\frac{\mu \beta }{\lambda }\frac{{{t}_{1}}}{{{t}_{2}}}\]
done
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C)
\[\frac{\beta \left( \mu -1 \right)}{\lambda }\left( {{t}_{1}}-{{t}_{2}} \right)\]
done
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D)
\[\left( \mu -1 \right)\frac{\lambda }{\beta }\left( {{t}_{1}}+{{t}_{2}} \right)\]
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question_answer15) This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: In an adiabatic process, change in internal energy of a gas is equal to work done on/by the gas in the process. Statement 2: The temperature of a gas remains constant in an adiabatic process.
JEE Main Online Paper (Held On 07 May 2012)
A)
Statement 1 is true. Statement 2 is true, Statement 2 is a correct explanation of Statement 1.
done
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B)
Statement 1 is true. Statement 2 is false.
done
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C)
Statement 1 is false, Statement 2 is true.
done
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D)
Statement 1 is false. Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
done
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question_answer16) This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: The possibility of an electric bulb fusing is higher at the time of switching ON. Statement 2: Resistance of an electric bulb when it is not lit up is much smaller than when it is lit up.
JEE Main Online Paper (Held On 07 May 2012)
A)
Statement 1 is true. Statement 2 is false
done
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B)
Statement 1 is false, Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
done
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C)
Statement 1 is true, Statement 2 is true, Statement 2 is a correct explanation of Statement 1.
done
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D)
Statement 1 is false, Statement 2 is true.
done
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question_answer17) Given that K= energy, V= velocity, T= time. If they are chosen as the fundamental units, then what is dimensional formula for surface tension?
JEE Main Online Paper (Held On 07 May 2012)
A)
\[[K{{V}^{-2}}{{T}^{-2}}]\]
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B)
\[[{{K}^{2}}{{V}^{2}}{{T}^{-2}}]\]
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C)
\[[{{K}^{2}}{{V}^{-2}}{{T}^{-2}}]\]
done
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D)
\[[K{{V}^{2}}{{T}^{2}}]\]
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question_answer18) A particle gets displaced by\[\Delta \over line{r}=\left( 2\hat{i}+3\hat{j}+4\hat{k} \right)m\]under the action of a force\[\vec{F}=\left( 7\hat{i}+4\hat{j}+3\hat{k} \right).\]The change in its kinetic energy is
JEE Main Online Paper (Held On 07 May 2012)
A)
38 J
done
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B)
70J
done
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C)
52.5 J
done
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D)
126 J
done
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question_answer19)
Two circuits (a) and (b) have charged capacitors of capacitance C, 2C and 3C with open switches. Charges on each of the capacitor are as shown in the figures. On closing the switches 
JEE Main Online Paper (Held On 07 May 2012)
A)
No charge flows in (a) but charge flows from R to L in (b)
done
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B)
Charges flow from L to R in both (a) and (b)
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C)
Charges flow from R to L in (a) and from L to R in(b)
done
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D)
No charge flows in (a) but charge flows from L to R in (b)
done
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question_answer20)
In an LCR circuit shown in the following figure, what will be the readings of the voltmeter across the resistor and ammeter if an a.c. source of 220Vand 100 Hz is connected to it as shown? 
JEE Main Online Paper (Held On 07 May 2012)
A)
800V,8A
done
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B)
110V.1.1A
done
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C)
300V, 3 A
done
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D)
220V, 2.2 A
done
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question_answer21) This question has Statement land Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: In the resonance tube experiment, if the tuning fork is replaced by another identical turning fork but with its arm having been filled, the length of the air column should be increased to obtain resonance again. Statement 2: On filling the arms, the frequency of a tuning fork increases.
JEE Main Online Paper (Held On 07 May 2012)
A)
Statement 1 is true. Statement 2 is true, Statement 2 is a correct explanation of Statement 1.
done
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B)
Statement 1 is true, Statement 2 is false.
done
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C)
Statement 1 is false, Statement 2 is true.
done
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D)
Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
done
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question_answer22) A bar magnet of length 6 cm has a magnetic moment of \[4J\,{{T}^{-1}}.\]Find the strength of magnetic field at a distance of 200 cm from the centre of the magnet along its equatorial line.
JEE Main Online Paper (Held On 07 May 2012)
A)
\[4\times {{10}^{-8}}\text{tesla}\]
done
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B)
\[3.5\times {{10}^{-8}}\text{tesla}\]
done
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C)
\[5\times {{10}^{-8}}\text{tesla}\]
done
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D)
\[3\times {{10}^{-8}}\text{tesla}\]
done
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question_answer23)
The load versus elongation graphs for four wires of same length and made of the same material are shown in the figure. The thinnest wire is represented by the line 
JEE Main Online Paper (Held On 07 May 2012)
A)
OA
done
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B)
OC
done
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C)
OD
done
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D)
OB
done
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question_answer24)
In the Rutherford experiment, a-particles are scattered from a nucleus as shown. Out of the four paths, which path is not possible? 
JEE Main Online Paper (Held On 07 May 2012)
A)
D
done
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B)
B
done
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C)
C
done
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D)
A
done
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question_answer25) The electric potential V(x) in a region around the origin is given by \[V(x)=4{{x}^{2}}\]volts. The electric charge enclosed in a cube of 1 m side with its centre at the origin is (in coulomb).
JEE Main Online Paper (Held On 07 May 2012)
A)
\[8{{\varepsilon }_{0}}\]
done
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B)
\[-4{{\varepsilon }_{0}}\]
done
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C)
0
done
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D)
(d)\[-8{{\varepsilon }_{0}}\]
done
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question_answer26) Two polaroids have their polarizing directions parallel so that the intensity of a transmitted light is maximum. The angle through which either Polaroid must be turned if the intensity is to drop by one-half is
JEE Main Online Paper (Held On 07 May 2012)
A)
\[135{}^\circ \]
done
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B)
\[90{}^\circ \]
done
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C)
\[120{}^\circ \]
done
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D)
\[180{}^\circ \]
done
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question_answer27) Which of the following processes play a part in the formation of a rainbow? (i) Refraction (ii) Total internal reflection (iii) Dispersion (iv) Interference
JEE Main Online Paper (Held On 07 May 2012)
A)
(i),(ii)and(iii)
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B)
(i)and(ii)
done
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C)
(i), (ii) and (iv)
done
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D)
(iii) and (iv)
done
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question_answer28) A sample originally contained 1020 radioactive atoms, which emit a-particles. The ratio of \[\text{ }\!\!\alpha\!\!\text{ -}\]particles emitted in the third year to that emitted during the second year is 0.3. How many \[\text{ }\!\!\alpha\!\!\text{ -}\]particles were emitted in the first year?
JEE Main Online Paper (Held On 07 May 2012)
A)
\[3\times {{10}^{18}}\]
done
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B)
\[3\times {{10}^{19}}\]
done
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C)
\[5\times {{10}^{18}}\]
done
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D)
\[7\times {{10}^{19}}\]
done
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question_answer29) A solid sphere having mass m and radius r rolls down an inclined plane. Then its kinetic energy is
JEE Main Online Paper (Held On 07 May 2012)
A)
\[\frac{5}{7}\]rotational and \[\frac{2}{7}\]translational
done
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B)
\[\frac{2}{7}\]rotational and \[\frac{5}{7}\]translational
done
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C)
\[\frac{2}{5}\]rotational and \[\frac{3}{5}\]translational
done
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D)
\[\frac{1}{2}\]rotational and \[\frac{1}{2}\]translational
done
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question_answer30)
Which logic gate with inputs A and B performs the same operation as that performed by the following circuit? 
JEE Main Online Paper (Held On 07 May 2012)
A)
NAND gate
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B)
OR gate
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C)
NOR gate
done
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D)
AND gate
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