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CBSE

Subject

Physics

Class

JEE Class 12

JEE Physics 2009 Exam Questions

Multiple Choice Questions

1.

One kg of a diatomic gas is at a pressure of 8 × 104 N/m2 . The density of the gas is 4 kg/m-3. What is the energy of the gas due to its thermal motion?

  • 3 × 104 J

  • 5× 104 J

  • 6× 104 J

  • 7× 104 J


B.

5× 104 J

Thermal energy corresponds to internal energy
Mass = 1 kg
density = 8 kg/m3
Volume space equals space mass over density space equals space 1 over 8 straight m cubed
Pressure space equals space 8 space straight x space 10 to the power of 4 space straight N divided by straight m squared
Therefore comma space Internal space Energy space equals space 5 over 2 space space straight P space straight x space straight V space equals space 5 space straight x 10 to the power of 4 space straight J

667 Views

2.

Let P(r) = Qr/πR4 be the charge density distribution for a solid sphere of radius R and total charge Q. for a point ‘p’ inside the sphere at distance r1 from the centre of the sphere, the magnitude of electric field is

  • fraction numerator straight Q over denominator 4 πε subscript straight o straight r subscript 1 superscript 2 end fraction
  • 0

  • fraction numerator Qr subscript 1 superscript 2 over denominator 4 πε subscript straight o straight R to the power of 4 end fraction
  • fraction numerator Qr subscript 1 superscript 2 over denominator 3 πε subscript straight o straight R to the power of 4 end fraction

C.

fraction numerator Qr subscript 1 superscript 2 over denominator 4 πε subscript straight o straight R to the power of 4 end fraction
fraction numerator straight Q over denominator 4 πε subscript 0 straight r subscript 1 superscript 2 end fraction space integral subscript straight r space equals 0 end subscript superscript straight r subscript 1 end superscript space fraction numerator 4 space πr cubed dr over denominator πR to the power of 4 end fraction
space equals space fraction numerator straight Q over denominator 4 πε subscript 0 end fraction fraction numerator straight r subscript 1 superscript 2 over denominator straight R subscript 4 end fraction
626 Views

3.

A thin uniform rod of length

  • 1 third fraction numerator calligraphic l squared straight omega squared over denominator straight g end fraction
  • 1 over 6 fraction numerator calligraphic l straight omega over denominator straight g end fraction
  • 1 half fraction numerator calligraphic l squared straight omega squared over denominator straight g end fraction
  • 1 over 6 fraction numerator calligraphic l squared straight omega squared over denominator straight g end fraction

D.

1 over 6 fraction numerator calligraphic l squared straight omega squared over denominator straight g end fraction
1 half open parentheses fraction numerator straight m space calligraphic l squared over denominator 3 end fraction close parentheses straight omega squared space equals space mgh
rightwards double arrow space straight h space equals space fraction numerator straight omega squared calligraphic l squared over denominator 6 straight g end fraction
251 Views

4.

If x, v and a denote the displacement, the velocity and the acceleration of a particle executing simple harmonic motion of time period T, then, which of the following does not change with time?

  • a2T2+ 4π2v2

  • aT/x

  • aT + 2πv

  • aT/v 


B.

aT/x

747 Views

5.

Consider a rubber ball freely falling from a height h = 4.9 m onto a horizontal elastic plate.Assume that the duration of collision is negligible and the collision with the plate is totally elastic.Then the velocity as a function of time and the height as a function of time will be


C.

When ball strikes the surface its velocity will be reversed therefore correct answer is 3.

278 Views

6.

A particle has an initial velocity of 3 space stack straight i space with hat on top plus space 4 space stack straight j space with hat on top and an acceleration of It speed 0.4 space stack straight i space with hat on top plus space 0.3 space stack straight j space with hat on topafter 10 s

  • 10 units

  • 7 space square root of 2
  • 7 units

  • 8.5 units


B.

7 space square root of 2
straight V with rightwards arrow on top space equals straight u with rightwards arrow on top space plus straight a with rightwards arrow on top straight t
straight V with rightwards arrow on top space space equals space left parenthesis 3 straight i with hat on top space plus 4 space straight j with hat on top right parenthesis space plus space 10 left parenthesis 0.4 space straight i with hat on top space plus 0.3 space straight j with hat on top right parenthesis
straight V with rightwards arrow on top space equals 7 space straight i with hat on top space plus 7 straight j with hat on top space
rightwards double arrow space vertical line straight V with rightwards arrow on top vertical line space equals space 7 square root of 2
127 Views

7.

In an experiment, the angles are required to be measured using an instrument. 29 divisions of the main scale exactly coincide with the 30 divisions of the vernier scale. If the smallest division of the main scale is half–a–degree (= 0.5o° ), then the least count of the instrument is

  • one minute

  • half minute

  • One degree

  • half degree


A.

one minute

1VSD = 29/30 MSD
L.C. = 1 MSD – 1 VSD
= 1/30 MSD
1 over 30 space straight x 0.5 space equals space 1 over 60 space space equals space one space minute

295 Views

8.

A motorcycle starts from rest and accelerates along a straight path at 2 m/s2. At the straight point of the motorcycle, there is a stationary electric siren. How far has the motorcycle gone when the driver hears the frequency of the siren at 94% of its value when the motorcycle was at rest?

  • 49 m

  • 98 m

  • 147 m

  • 196 m


B.

98 m

straight V space equals space square root of 2 aS end root space equals space square root of 4 straight S end root
also comma space 94 space equals space 100 space open parentheses fraction numerator 330 minus straight V over denominator 330 end fraction close parentheses
rightwards double arrow fraction numerator 33 space straight x space 6 over denominator 10 end fraction space equals space square root of 4 straight S end root
rightwards double arrow straight S space equals 98 space straight m
225 Views

9.

The height at which the acceleration due to gravity becomes g/9 (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth, is

  • 2R

  • fraction numerator straight R over denominator square root of 2 end fraction
  • R/2

  • square root of 2 straight R end root

A.

2R

fraction numerator GM over denominator 9 straight R squared end fraction space equals space fraction numerator GM over denominator left parenthesis straight R plus straight h right parenthesis squared end fraction
rightwards double arrow space 3 straight R space equals space straight R plus straight h
rightwards double arrow space straight h equals space 2 straight R
157 Views

10.

Two points P and Q are maintained at the potential of 10V and -4V respectively. The work done in moving 100 electrons from P to Q is 

  • 9.60 × 10–17

  • 9.60 × 10–17 J

  • – 2.24 × 10–16

  • 2.24 × 10–16 J


D.

2.24 × 10–16 J

W = QdV = Q(Vq - VP)
= -100 × (1.6 × 10-19) × (– 4 – 10)
= + 100 × 1.6 × 10-19 × 14 = +2.24 10-16 J

218 Views

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