A ball of mass m is projected from a horizontal surface with a speed u at an angle  $\theta$ with horizontal. Then ( $\widehat{i}and\widehat{j}$  are unit vector along horizontal and vertical)

a) The change in velocity between point of projection and maximum height is  $u\sin \theta (-\widehat{j})$

b) The change in velocity during its flight is  $2u\sin \theta (-\widehat{j})$

c) Average velocity during its flight is  $u\cos \theta \left(\widehat{i}\right)$

d) Average velocity during its half of time of flight is  $u\cos \theta \left(\widehat{i}\right)$

The correct statements from above are