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6. A BTwo containers A & B contain ideal gases heliumand oxygen respectively. Volume of both containersare equal and pressure is also equal. Container A hastwice the number of molecules than container B thenif v A & v B represent the rms speed of gases incontainers A & B respectively, then -(A)(C)vvvvABAB= 2 (B)= 2 (D)vvvvABAB= 4= 87. A capacitor is composed of three parallel conductingplates. All three plates are of same area A. The first pairof plates are kept a distance d 1 apart and the spacebetween them is filled with a medium of a dielectric ε 1 .The corresponding data for the second pair are d 2 & ε 2respectively. What is the surface charge density on themiddle plate ?d 1 d 2(A) ε0ε 1 ε 2V 0V ⎡ ε1ε2⎤⎢ + ⎥⎣d1d(B) ⎡ ε1ε2− ε ⎢ + ⎥ ⎤0V2 ⎦ ⎣d1d2⎦⎡ ε1ε2⎤⎡ ε1ε2⎤(C) 2 ε0V⎢+ ⎥ (D) − 2 ε0V⎢+ ⎥⎣d1d2⎦ ⎣d1d2⎦8. The mirror of length 2l makes 10 revolutions perminute about the axis crossing its mid point O andperpendicular to the plane of the figure There is alight source in point A and an observer at point B ofthe circle of radius R drawn around centreO (∠AOB = 90º)(A) 2 (B)l12OψAlRB(C) 2 2 (D)SECTION – IIMultiple Correct Answers TypeThis section contains 4 multiple correct answer(s) typequestions. Each question has 4 choices (A), (B), (C) and(D), out of which ONE OR MORE is/are correct.9. A body moves in a circular path of radius R withdeceleration so that at any moment of time itstangential and normal acceleration are equal inmagnitude. At the initial moment t = 0, the velocityof body is v 0 then the velocity of body at any timewill be –v0(A) v = at time t⎛ v t ⎞⎜1+0⎟⎝ R ⎠SR(B) v = v0e− after it has moved S meter(C) v = v 0 e –SR after it has moved S meter(D) None of these10. A cylinder block of length L = 1m is in twoimmiscible liquids. Part of block inside liquid(1) is1 1 m and in liquid (2) is m. Area of cross-section44of block is A. Densities of liquid (1) & (2) are ρ and2ρ respectively –ρ.Liquid (1)212What is the proportion lR if the observer B first seesthe light source when the angle of mirrorψ = 15º ?2ρ.Liquid (2)XtraEdge for IIT-JEE 59APRIL 2010