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WBJEE | 2011
Q. A box is moved along a straight line by machine delivering constant power. The distance moved by the body in time t is proportional to:
  1. t2
  2. t32
  3. t34
  4. t12
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Q. A cubical vessel of height 1m is full of water. What is the amount of work done in pumping water out of the vessel?
(Take g=10m/s2)
  1. 1250 J
  2. 5000 J
  3. 1000 J
  4. 2500 J
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Q. An object weights m1 in a liquid of density d1 and that in liquid of density d2 is m2. The density d of the object is
  1. m2d2m1d1m2m1
  2. m1d1m2d2m2m1
  3. m2d1m1d2m1m2
  4. m1d2m2d1m1m2
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Q. A stone of relative density K is released from rest on the surface of a lake. If viscous effect are ignored, the stone sinks in water with an acceleration of:
  1. g(1K)
  2. g(1+1K)
  3. g(1+K)
  4. g(11K)
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Q. A material has Poisson's ratio 0.50. If a uniform rod of it suffers a longitudinal strain of 2×103, then the percentage change in volume is
  1. 0.6
  2. 0.4
  3. zero
  4. 0.2
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Q. The resistance across A and B in the given figure will be:
467016.png
  1. None of the above
  2. 3R
  3. R3
  4. R
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Q. Two identical cylindrical vessels, with their bases at the same level, each contain a liquid of density ρ. The height of liquid in one vessel in h1 and that in the other is h2. The area of either base is A. What is the work done by gravity in equalising the levels when the vessels are interconnected?
  1. Aρg(h1h22)2
  2. Aρg(h1+h22)2
  3. 12Aρg(h1h2)2
  4. None of these
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Q. Tow identical springs are connected to mass m as shown (k= spring constant). IF the period of the configuration in (a) is 2s, the period of the configuration in (b) is
467481.png
  1. 2s
  2. 22s
  3. 12s
  4. 1s
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Q. Two cells with the same emf E and different internal resistances r1 and r2 are connected in series to an external resistance R. The value of R so that the potential difference across the first cell be zero, is
  1. r1r2
  2. r1r2
  3. r1+r2
  4. r1+r22
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Q. If g is the acceleration due to gravity on the surface of the earth, the gain in potential energy of an object of mass m raised from the earth's surface to a height equal to the radius R of the earth is
  1. mgR4
  2. mgR2
  3. mgR
  4. 2mgR
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Q. The charge on the capacitor of capacitance C shown in the figure will be :
467015.png
  1. CER1R2+r
  2. CER1R1+r
  3. CE
  4. CER2R2+r
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Q. A shell of mass m is at rest initially. It explodes into three fragments having masses in the ratio 2:2:1. The fragments having equal masses fly off along mutually perpendicular direction with speed v. What will be the speed of the third (lighter) fragment?
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Q. If a person can throw a stone to maximum height of h metre vertically, then the maximum distance through which it can be thrown horizontally by the same person is
  1. h
  2. 3h
  3. 2h
  4. h2
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Q. A small spherical ball of mass m slides without friction from the top of a hemisphere of radius R. At what height will the ball lose contact with surface of the sphere?
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Q. Which type of gate the following truth table represents?
InputInputOutput
ABQ
001
011
101
110

  1. NOT
  2. OR
  3. AND
  4. NAND
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Q. A body of mass 6kg is acted upon by a force which causes a displacement in it given by x=t24 metre, where t is the time in second. The work done by the force in 2s is
  1. 12J
  2. 9J
  3. 6J
  4. 3J
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Q. In the nuclear reaction, 147N+X146C+11H, the X will be
  1. 01e
  2. 10n
  3. 11H
  4. 21H
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Q. Current through ABC and ABC is I. What is the magnetic field at P?
(Given, BP=PB=r and CBPBC are colinear)

467080.PNG
  1. B=14π(2Ir)
  2. B=μ04π(2Ir)
  3. B=μ04π(Ir)
  4. Zero
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Q. A body floats in water with 40% of its volume outside water. When the same body floats in an oil 60% of its volume remains outside oil. The relative density of oil is:
  1. 0.9
  2. 1.2
  3. 1.0
  4. 1.5
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Q. The magnetic field at the point of intersection of diagonals of a square wire loop side L carrying a current I is
  1. μ0IπL
  2. 2μ0IπL
  3. 2μ0IπL
  4. 22μ0IπL
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Q. Given A=2^i+3^j and B=^i+^j. The component of vector A along vector B is:
  1. 12
  2. 52
  3. 72
  4. 32
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Q. A particle is moving with constant speed v in circle. What is the magnitude of average velocity after half rotation?
  1. 2vπ
  2. 2v
  3. v2
  4. v2π
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Q. A radioactive nucleus of mass number A, initially at rest, emits an α-particle with a speed v. The recoil speed of the daughter nucleus will be
  1. 2vA+4
  2. 2vA4
  3. 4vA4
  4. 4vA+4
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Q. A battery of emf E and identical resistance r is connected across a pure resistive device (such as an electric heater) of resistance R. Prove that the power output of the device will be maximum if R=r.
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Q. Two soap bubbles of radii x and y coalesce to constitute a bubble of radius z. Then z is equal to:
  1. x2+y2
  2. x+y
  3. x+y2
  4. x+y
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Q. A cricket ball of mass 0.25kg with speed 10m/s collides with a bat and returns with same speed within 0.01s. The force acted on bat is
  1. 25 N
  2. 250 N
  3. 50 N
  4. 500 N
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Q. Five equal resistance, each of resistance R are connected as shown in figure. A battery of V volt is connected between A and B. The current flowing in FC will be
467018.PNG
  1. 3VR
  2. V2R
  3. 2VR
  4. VR
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Q. In an inelastic collision an electron excites a hydrogen atom from its ground state to a M-shell state. A second electron collides instantaneously with the excited hydrogen atom in the M-shell state and ionizes it. At least how much energy the second electron transfers to the atom in the M-shell state?
  1. +3.4eV
  2. +1.51eV
  3. 3.4eV
  4. 1.51eV
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Q. A radioactive isotope X with half life 1.5×109yr decays into a stable nucleus Y. A rock sample contains both elements X and Y in ratio 1:15. Find the age of the rock
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Q. If the earth were to suddenly contract to 1nth if its present radius without any change in its mass, the duration of the new day will be nearly
  1. 24n hr
  2. 24n2 hr
  3. 24n2 hr
  4. 24n hr
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