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

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

A body is projected horizontally with a velocity 4$\sqrt{2}$  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

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.

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

175.

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

• 

• 

• 

• 

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

If vectors  $\overrightarrow{\mathrm{P}} = \mathrm{a}\hat{\mathrm{i}} + \mathrm{a}\hat{\mathrm{j}} + 3\hat{\mathrm{k}}$  and  $\overrightarrow{\mathrm{Q}} = \mathrm{a}\hat{\mathrm{i}} - 2\hat{\mathrm{j}} - \hat{\mathrm{k}}$ are perpendicular to each other, then the positive value of  a  is

• 3

• 1

• 2

• 0

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

• 0^°

• 90^°

• ^45°

• 180^°

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 $\times$10⁸ m/s²

• 8 $\times$10⁵ m/s²

• 120$\times$ 10⁵ m/s²

• 4 $\times$ 10⁸ m/s²

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