$A$ 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 ......... $N$.

The magnitude of the external force acting on moving bodies can be known directly by

State and explain Newton's second law of motion. Write its important points.

At any instant,the velocity of a particle of mass $500 \, g$ is $(2t \hat{i} + 3t^2 \hat{j}) \, ms^{-1}$. If the force acting on the particle at $t = 1 \, s$ is $(\hat{i} + x \hat{j}) \, N$,then the value of $x$ will be:

$A$ 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 $\,m/s$)?

$A$ body of $5 \, kg$ is moving with a velocity of $20 \, m/s$. If a force of $100 \, N$ is applied on it for $10 \, s$ in the same direction as its velocity,what will be the final velocity of the body in $m/s$?