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CBSE

Subject

Physics

Class

JEE Class 12

JEE Physics 2008 Exam Questions

Multiple Choice Questions

1.

The dimension of magnetic field in M, L, T and C (Coulomb) is given as

  • MLT−1C−1

  • MT2C−2

  • MT−1C−1

  • MT−2C−1


C.

MT−1C−1

F = qvB
B = F/qv
= MC−1 T−1

176 Views

2.

A body of mass m = 3.513 kg is moving along the x-axis with a speed of 5.00 ms−1.The magnitude of its momentum is recorded as

  • 17.6 kg ms−1 

  • 17.565 kg ms−1

  • 17.56 kg ms−1

  • 17.57 kg ms−1


A.

17.6 kg ms−1 

P = mv = 3.513 × 5.00 ≈ 17.6

184 Views

3.

A planet in a distant solar system is 10 times more massive than the earth and its radius is 10 times smaller. Given that the escape velocity from the earth is 11 kms−1, the escape velocity from the

  • 1.1 kms−1

  • 11 kms−1

  • 110 kms−1

  • 0.11 kms−1


C.

110 kms−1

straight V subscript esc space equals space square root of fraction numerator 2 GM over denominator straight R end fraction end root space equals space square root of fraction numerator 2 straight G space straight x space 10 space straight M over denominator straight R divided by 10 end fraction end root space
space equals space 10 space straight x space 11 space equals space 110 space km divided by straight s
651 Views

4.

Consider a uniform square plate of side ‘a’ and mass ‘m’. The moment of inertia of this plate about an axis perpendicular to its plane and passing through one of its corners is

  • (5/6)ma2

  • (1/12)ma2

  • (7/12)ma2

  • (2/3)ma2


D.

(2/3)ma2

straight I space equals straight I subscript cm space plus space straight m open parentheses fraction numerator straight a square root of 2 over denominator 2 end fraction close parentheses squared space equals space ma squared over 6 space plus ma squared over 2
space equals space 2 over 3 ma squared
978 Views

5.

This question contains Statement -1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement – I:
For a mass M kept at the centre of a cube of side ‘a’, the flux of gravitational field passing through its sides is 4π GM.
and
Statement – II
If the direction of a field due to a point source is radial and its dependence on the distance ‘r’ for the source is given as 1/r2, its flux through a closed surface depends only on the strength of the source enclosed by the surface and not on the size or shape of the surface

  • Statement – 1is false, Statement – 2 is true.

  • Statement – 1is true, Statement – 2 is true; Statement -2 is correct explanation for Statement-1.

  • Statement – 1 is true, Statement – 2 is true; Statement -2 is not a correct explanation for Statement-1.

  • Statement – 1 is true, Statement – 2 is False. 


B.

Statement – 1is true, Statement – 2 is true; Statement -2 is correct explanation for Statement-1.

g = GM/r2

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6.

A block of mass 0.50 kg is moving with a speed of 2.00 m/s on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

  • 0.16 J

  • 1.00 J

  • 0.67 J

  • 0.34 J


C.

0.67 J

m1u1 + m2u2 = (m1 + m2)v
v = 2/3 m/s
Energy space loss space equals space 1 half space left parenthesis 0.5 right parenthesis space straight x space left parenthesis 2 right parenthesis squared space minus space 1 half space left parenthesis 1.5 right parenthesis space straight x space open parentheses 2 over 3 close parentheses squared
space equals space 0.67 space straight J

183 Views

7.

Two full turns of the circular scale of a screw gauge cover a distance of 1 mm on its main scale. The total number of divisions on the circular scale is 50. Further, it is found that the screw gauge has a zero error of − 0.03 mm while measuring the diameter of a thin wire, a student notes the main scale reading of 3 mm and the number of circular scale divisions in line with the main scale as 35. The diameter of the wire is 

  • 3.32 mm

  • 3.73 mm

  • 3.67 mm

  • 3.38 mm


D.

3.38 mm

Diameter = M.S.R. + C.S.R × L.C. + Z.E.
= 3 + 35 × (0.5/50) + 0.03 = 3.38 mm 

207 Views

8.

A thin rod of length ‘L’ is lying along the x-axis with its ends at x = 0 and x = L. Its linear density (mass/length) varies with x as,straight k space open parentheses straight x over straight L close parentheses to the power of straight n where n can be zero or any positive number. If the position xCM of the centre of mass of the rod is plotted against ‘n’, which of the following graphs best approximates the dependence of xCM on n? 


A.

space straight x subscript cm space equals space fraction numerator integral dmx over denominator integral dm end fraction
fraction numerator integral begin display style λdx end style begin display style. end style begin display style straight x end style over denominator integral begin display style dm end style end fraction
space equals space fraction numerator integral begin display style straight k end style begin display style begin display style open parentheses straight x over straight L close parentheses end style squared end style begin display style. end style begin display style xdx end style over denominator straight k open parentheses begin display style straight x over straight L end style close parentheses to the power of straight n space dx end fraction
space equals space open square brackets fraction numerator begin display style fraction numerator kx to the power of straight n plus 2 end exponent over denominator left parenthesis straight n plus 2 right parenthesis straight L to the power of straight n end fraction end style over denominator begin display style fraction numerator kx to the power of straight n plus 1 end exponent over denominator left parenthesis straight n plus 1 right parenthesis straight L to the power of straight n end fraction end style end fraction close square brackets subscript 0 superscript straight L
space equals space open square brackets fraction numerator straight x left parenthesis straight n plus 1 right parenthesis over denominator straight n plus 2 end fraction close square brackets subscript 0 superscript straight L
straight x subscript cm space equals space straight L over 2 comma fraction numerator 2 straight L over denominator 3 end fraction comma fraction numerator 4 straight L over denominator 5 end fraction comma fraction numerator 5 straight L over denominator 6 end fraction comma.....
325 Views

9.

An athlete in the Olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

  • 200 J − 500 J

  • 2 × 105J − 3 × 105J

  •  20,000 J − 50,000 J

  • 2,000 J − 5,000 J


C.

 20,000 J − 50,000 J

Approximate mass = 60 kg Approximate
velocity = 10 m/s Approximate
KE = (1/2)x60 x1000 = 3000 J
= KE range ⇒ 2000 to 5000 joule

346 Views

10.

A body is at rest at x = 0. At t = 0, it starts moving in the positive x-direction with a constant acceleration. At the same instant another body passes through x = 0 moving in the positive x-directionn with a constant speed. The position of the first body is given by x1(t) after time ‘t’ and that of the second body by x2(t) after the same time interval. Which of the following graphs correctly describes (x1 – x2)as a function of time ‘t’?


B.

straight x subscript 1 space left parenthesis straight t right parenthesis space equals space 1 half space at squared
straight x subscript 2 space left parenthesis straight t right parenthesis space equals space vt
straight x subscript 1 minus straight x subscript 2 space equals space 1 half at squared space minus vt
339 Views

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