Newton's second law of motion gives us a measure of

An object experiences a net zero external unbalanced force. Is it possible for the object to be moving with a non-zero velocity? If yes,state the conditions that must be placed on the magnitude and direction of the velocity. If no,provide a reason.

Show that the rate of change of momentum $=$ mass $\times$ acceleration.

$A$ truck starts from rest and rolls down a hill with constant acceleration. It travels a distance of $400 \, m$ in $20 \, s$. Find its acceleration. Find the force acting on it, if its mass is $7$ metric tons.

Name the physical quantity whose $SI$ unit is "newton".

Two cars each of mass $1000 \ kg$ are moving in a straight line but in opposite directions. The velocity of each car is $5 \ m s^{-1}$ before the collision during which they stick together. What will be the velocity of the combined cars after collision (in $m s^{-1}$)?