A projectile is projected with initial velocity $(6\hat{i}+8\hat{j}) \mathrm{m} {\mathrm{s}}^{-1}$, from the ground. The velocity when it is about to hit the ground is (assuming $y$-axis is along vertical direction)

A body is projected horizontally with speed $5 \mathrm{m} {\mathrm{s}}^{-1}$ from height $h,$ takes $8 \mathrm{s}$ to reach the ground. The time it takes to cover the first one fourth of height is

A particle is moving with constant speed $v$ in plane as shown in figure. The magnitude of the angular velocity about point $O$ is

A particle is moving eastwards with a speed of $6 \mathrm{m} {\mathrm{s}}^{-1}.$ After  $6 \mathrm{s},$ the particle is found to be moving with same speed in a direction $60°$ north of east. The magnitude of average acceleration in this interval . of time is