36) For a given velocity of a projectile, the range is maximum when the angle of projection is

37) The angle of projection at which the horizontal range and maximum height of a projectile are equal to

38) The maximum value of the horizontal range for a projectile projected with a velocity of 98 m/sec is

39) A stone is thrown vertically upwards with a vertical velocity of 49 m/sec. It returns to the ground in

40) A projectile has maximum range of 40 m on a horizontal plane. If angle of projection is a and the time of flight is 1 second, then sin a must be about