At a height $0.4\, m$ from the ground,the velocity of a projectile in vector form is $\vec v = (6\hat i + 2\hat j)\,m/s$. The angle of projection is ...... $^o$ $(g = 10\, m/s^2)$.

$A$ ball is rolled off the edge of a horizontal table at a speed of $4\, m/s$. It hits the ground after $0.4\, s$. Which statement given below is true?

$A$ boy playing on the roof of a $10 \, m$ high building throws a ball with a speed of $10 \, m/s$ at an angle $30^{\circ}$ with the horizontal. How far from the throwing point will the ball be at the height of $10 \, m$ from the ground (in $, m$)? $(g = 10 \, m/s^2, \sin 30^{\circ} = 1/2, \cos 30^{\circ} = \sqrt{3}/2)$

$A$ helicopter flying horizontally with a speed of $360 \ km/h$ at an altitude of $2 \ km$,drops an object at an instant. The object hits the ground at a point $O$,$20 \ s$ after it is dropped. The displacement of $O$ from the position of the helicopter where the object was released is: (use acceleration due to gravity $g = 10 \ m/s^2$ and neglect air resistance)

$A$ cannon ball is fired from the top of a $55 \ m$ high cliff with an initial speed of $50 \ m \ s^{-1}$. The speed of the cannon ball while hitting the ground in $m \ s^{-1}$ is (acceleration due to gravity $= 10 \ m \ s^{-2}$):

$A$ stone is projected from a point on the ground so as to hit a bird on the top of a vertical pole of height $h$ and then attain a maximum height $2h$ above the ground. If at the instant of projection the bird flies away horizontally with a uniform speed and if the stone hits the bird while descending,then the ratio of the speed of the bird to the horizontal speed of the stone is