The $SI$ unit of force is

Two objects of masses $100 \, g$ and $200 \, g$ are moving along the same line and direction with velocities of $2 \, m \, s^{-1}$ and $1 \, m \, s^{-1}$,respectively. They collide and after the collision,the first object moves at a velocity of $1.67 \, m \, s^{-1}$. Determine the velocity (in $m/s$) of the second object.

$A$ $8000 \,kg$ engine pulls a train of $5$ wagons,each of $2000 \,kg$,along a horizontal track. If the engine exerts a force of $40000 \,N$ and the track offers a friction force of $5000 \,N$,then calculate the acceleration (in $m/s^2$) of the train.

Chetan's father wanted to buy a car. He visited many showrooms to find out the price and the specifications of various cars. In one of the showrooms,he was told by the salesman that their car had excellent brakes such that the car stops instantaneously. Chetan's father was impressed and decided to buy that car. In the evening,he discussed this with his family. Chetan told his father that such a car cannot be made and the salesman had lied to him. He told his father that he should not buy that car and,moreover,never from that showroom. He explained to his father why it is not possible. His father was convinced and promised to visit another showroom and be careful this time.
$(a)$ What might have been the explanation given by Chetan to convince his father?
$(b)$ What values do you see in Chetan?

An automobile vehicle has a mass of $1500 \, kg$. What must be the force (in $N$) between the vehicle and road if the vehicle is to be stopped with a negative acceleration of $1.7 \, m \, s^{-2}$?

Two similar vehicles are moving with the same velocity on roads,such that one of them is loaded and the other is empty. Which of the two vehicles will require a larger force to stop it? Give reasons.