A scooter starts from rest moves in a straight line with a constant acceleration and covers a distance of $64 \,m$ in $4 \,s$

$(i)$ Calculate its acceleration and its final velocity.

$(ii)$ At what time the scooter had covered half the total distance ?

An artificial satellite is moving in a circular orbit of radius nearly $42.250 \,km .$ Calculate its linear velocity, if it takes $24$ hour to revolve round the earth.

Draw a velocity versus time graph of a stone thrown vertically upwards and then coming downwards after attaining the maximum height. 

A car starts from rest and moves along the $x-$ axis with constant acceleration $5\, ms^{-2}$ for $8\,\sec $. If it then continues with constant velocity, what distance will the car cover in $12\,\sec $ since it started from the rest ?

Give an expression for the speed of an athlete if he takes time $'t^{\prime}$ to go around a circular track, of radius ${ }^{\prime} r^{\prime}$