Question

A block of metal weighing $2\text{kg}$ is resting on a frictionless plane. It is struck by a jet releasing water at a rate of $1\text{kg/s}$ and a speed of $5\text{m/s}$. The initial acceleration of the block in ${\text{m/s}}^2$ will be

Answer 1

The water jet striking the block at the rate of $1\text{kg/s}$ at a speed of $5\text{m/s}$ will exert a force on the block
$F=v\frac{dm}{dt}=5\times 1=5\text{N}$
Under the action of this force of $5\text{N}$, the block of mass $2\text{kg}$ will move with an acceleration given by
$a=\frac{F}{m}=\frac{5}{2}=2.5{\text{m/s}}^2$