When a body is acted upon by a constant force,then which of the following quantities remains constant?

$A$ body under the action of a force $\vec{F} = 6\hat{i} - 8\hat{j} \text{ N}$ acquires an acceleration of $5 \text{ m s}^{-2}$. The mass of the body is ........ $\text{kg}$.

$A$ body of mass $10 \,kg$ is acted upon by a force given by the equation $F = (3t^2 - 30) \,N$. The initial velocity of the body is $10 \,m/s$. What is the velocity of the body after $5 \,s$ (in $\,m/s$)?

The engine of a jet aircraft applies a thrust force of $10^5\, N$ during take-off and causes the plane to attain a velocity of $1\, km/s$ in $10\, s$. The mass of the plane is:

$A$ body of mass $2\, kg$ travels according to the law $x = at + bt^2 + ct^3$,where $a = 3\, m/s$,$b = 4\, m/s^2$,and $c = 5\, m/s^3$. The force acting on the body at $t = 2\, s$ is ......... $N$.

$A$ force of $100 \, dynes$ acts on a mass of $5 \, g$ for $10 \, s$. The velocity produced is ......... $cm/s$.