Assertion:  Generally  the  path  of  a&

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 Multiple Choice QuestionsMultiple Choice Questions

171.

Assertion: In javelin throw, the athlete throws the projectile at an angle slightly more than 45o.

Reason: The maximum range does not depend upon the angle of projection.

  • If both assertion and reason are true and reason is the correct explanation of assertion. 

  • If both assertion and reason are true and reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false


172.

A body is projected horizontally with a velocity 42  m/sec. The velocity of the body after 0.7 seconds will be nearly ( Take g = 10 m/sec2 )

  • 10 m/sec

  • 9 m/sec

  • 19 m/sec

  • 11 m/sec


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173.

Assertion:  Generally  the  path  of  a  projectile from  the  earth  is  parabolic  but  it  is elliptical  for  projectiles  going  to  a very  great  height.

Reason:  Up to ordinary height the  projectile  moves under  a  uniform  gravitational  force, but  for  great  heights,  projectile  moves  under a  variable force.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion

Upto  ordinary  heights  the  change  in  the distance  of  a  projectile  from  the  centre of the  earth is  negligible  compared  to  the  radius  of  the  earth. Hence  projectile  moves under a  nearly  uniform gravitational  force  and its  path  is parabolic. But  for  projectiles going  to  great  heights , the  gravitational  force  decreases  in  inverse  poroportion  to the  square  of the  distance  of  the  projectile  from  the  centre  of  the  earth. Under such  a  variable  force  the  path  of projectile  is  elliptical.


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174.

Assertion: When the velocity of projection of a body is made  n times, its time of flight becomes n  times.

Reason: Range of projectile does not depend on
the initial velocity of a body.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


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175.

Which of the following velocity-time graphs shows a realistic situation for a body in motion?


176.

A lead shot of  1 mm diameter falls through a long column of glycerine. The variation of its velocity  'v'  with distance covered is represented by


177.

If vectors  P = ai^ + aj^ + 3k^  and  Q = ai^ - 2j^ - k^ are perpendicular to each other, then the positive value of  a  is

  • 3

  • 1

  • 2

  • 0


178.

At the uppermost point of a projectile, its velocity and acceleration are at an angle of

  • 0°

  • 90°

  • 45°

  • 180°


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179.

Certain neutron stars are believed to be rotating at about 1 rev/s. If such a star has a radius of 20 km, the acceleration of an object on the equator of the star will be

  • 20 ×108 m/s2

  • ×105 m/s2

  • 120× 105 m/s2

  • × 108 m/s2


180.

In a carnival ride, the passengers travel in a circle of radius 5.0 m, making one complete circle in 4.0 s. What is the acceleration?

  • 24.6 m/s2

  • 12.3 m/s2

  • 6.15 m/s2

  • 49.2 m/s2


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