If velocity and acceleration are in opposite directions in one-dimensional motion,what happens to the magnitude of velocity?

The acceleration of a train between two stations is shown in the figure. The maximum speed of the train is $............\,m/s$.

In what different ways can velocity be changed?

Motion of a particle is given by the equation $s = (3t^3 + 7t^2 + 3t + 8) \ m$. The acceleration of the particle at $t = 1 \ s$ is: (in $m/s^2$)

$A$ 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 is moving according to the equation $x = at + bt^2 - ct^3$,where $x$ is displacement and $a, b,$ and $c$ are constants. The acceleration of the body is: