What physical quantity is represented by the area under the force-time graph?

$A$ mass of $1 \ kg$ is suspended by a string $A$. Another string $C$ is connected to its lower end (see figure). If a sudden jerk is given to $C$,then

If impulse $I$ varies with time $t$ as $I \text{ (kg m s}^{-1}) = 20 t^2 - 40 t$. The change in momentum is minimum at ........... $s$.

What is impulse of force? Write its unit and dimension.

An engine pumps water continuously through a hose. Water leaves the hose with velocity $v$ and $m$ is the mass per unit length of the water jet. If this jet hits a surface and comes to rest instantaneously,the force on the surface is

$A$ force of $50 \, dynes$ acts on a particle of mass $5 \, g$ for $3 \, seconds$. What is the impulse of the force?