If $v$ is the velocity of a body moving along the $x$-axis,then the acceleration of the body is .........

What will be the change in the speed of a moving object if both speed and acceleration are positive or both are negative?

If the displacement ($s$ in metre) of a moving particle in terms of time ($t$ in second) is $s = t^3 - 6t^2 + 18t + 9$,then the minimum velocity attained by the particle is (in $m \ s^{-1}$)

Define acceleration,average acceleration,and instantaneous acceleration.

$Assertion$ : Retardation is directly opposite to the velocity.
$Reason$ : Retardation is equal to the time rate of decrease of speed.

The velocity of a body depends on time according to the equation $v = \frac{t^2}{10} + 20$. The body is undergoing