78. A projectile is fired at an angle 0 to the vertical. Its horizontal range will be maximum when 0 is

A. 0?

B. 30?

C., 45?

D. 60?

79. If the velocity of projection is 4 m/sec and the angle of projection is a?, the maximum height of the projectile from a horizontal plane, is

A.u2 cos2 a

B.u2 sin2 a

C.u2 tan2 a

D.u2 sin 2a

80. If a particle is projected inside a horizontal tunnel which is 554 cm high with a velocity of 60 m per sec, the angle of projection for maxi-mum range, is

A. 8?

B. 9?

C. 10?

D. 11?

81. If the angle of projection is double the angle of inclination (a) of the plane on which particle is projected, the ratio of times of fligh up the inclined plane and down the inclined plane, will be

A.2 cos a.

B.2 sin a

C. 2 cos a.

D.2 tan a

82. The angle of projection for a range is equal to the distance through which the particle would have fallen in order to acquire a velocity equal to the velocity of projection, will be

A. 30?

B. 45?

C. 60?

D. 75?.

83. The direction of projection should bisect the angle between the inclined plane and the vertical for a range of a projectile on inclined plane

A. to be zero

B. to be maximum

C. to be minimum

D. none of the these.

84. A body is said to move with Simple Harmonic Motion if its acceleration, is

A. always directed away from the centre, the point of reference

B. proportional to the square of the distance from the point of reference

C. proportional to the distance from the point of reference and directed towards it

D. inversely proportion to the distance from the point of /reference none of these.

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