What are the changes possible on an object at rest if we apply on it:
$(a)$ a balanced force?
$(b)$ an unbalanced force?

$A$ girl of mass $50 \, kg$ jumps out of a moving boat of mass $300 \, kg$ onto the bank with a horizontal velocity of $3 \, m s^{-1}$. With what velocity will the boat begin to move backwards (in $, m s^{-1}$)?

$A$ body of mass $500 \, g$ is at rest on a frictionless surface. Calculate the distance travelled by it in $10 \, s$ when acted upon by a force of $10^{-2} \, N$. (in $, m$)

Give reasons and state the laws related to these statements:
$(a)$ It is easier to push an empty box than to push a box full of books.
$(b)$ It is difficult for a fireman to hold a hose which ejects a large amount of water with high velocity.

Write answers to the following:
$(i)$ Mention the direction in which the force of friction acts on a moving body. State its units.
$(ii)$ Name the property of bodies (or objects) to resist a change in their state of rest or of motion. Name the quantity that is a measure of this property.
$(iii)$ Name the physical quantity whose unit is $kg\, m s^{-1}$. Define this quantity.

If a body experiences a net zero unbalanced force, then the body: