What is retardation? What is its direction?

$A$ particle is moving in a straight line such that its velocity is increasing at $5\,m/s$ per meter. The acceleration of the particle is .......... $m/s^2$ at a point where its velocity is $20\,m/s$.

$A$ body in one-dimensional motion has zero speed at an instant. At that instant,it must have:

Which physical quantity can be found by first differentiation and second differentiation of position vector?

In what different ways can velocity be changed?

The displacement is given by $x = 2t^2 + t + 5$. The acceleration at $t = 2 \ s$ is: