Can the speed of a body be negative?

$(a)$ Define acceleration.
$(b)$ $A$ stone describes a circular path with a constant speed. State the type of motion of the stone.

The displacement of a body is proportional to the cube of the time lapsed. The magnitude of the acceleration is

What determines the direction of motion of an object: velocity or acceleration?

$A$ motorbike running at a speed of $90\, km h^{-1}$ slows down to $18\, km h^{-1}$ in $2.5\, s$. Calculate:
$(i)$ Acceleration
$(ii)$ Distance covered during the deceleration

What is the nature of the displacement-time graph of a body moving with constant velocity?