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

$A$ 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 $\vec{F_1}$ of magnitude $4 \ N$ acts on an object of mass $1 \ kg$ at the origin in a direction $30^{\circ}$ above the positive $x$-axis. $A$ second force $\vec{F_2}$ of magnitude $4 \ N$ acts on the same object in the direction of the positive $y$-axis. The magnitude of the acceleration of the object is nearly: (in $m \ s^{-2}$)

From the following graph,find the magnitude of the negative force in $N$.

An object of mass $3\,kg$ is at rest. If a force $\vec{F} = (6t^2\hat{i} + 4t\hat{j})\,N$ is applied on the object,then the velocity of the object at $t = 3\,s$ will be

The average resisting force that must act on a $5 \,kg$ mass to reduce its speed from $65 \,cm/s$ to $15 \,cm/s$ in $0.2 \,s$ is .......... $N$.