B. Inertia and gravity must be balanced.
Acceleration no longer exist as the car stops.
Answer:

Explanation:
As we know that there is no external torque on the system of two disc
then the angular momentum of the system will remains conserved
So we will have

now we have

also we have

now from above equation we have

now we have


Answer:
The speed of the shell at launch and 5.4 s after the launch is 13.38 m/s it is moving towards the Earth.
Explanation:
Let u is the initial speed of the launch. Using first equation of motion as :

a=-g

The velocity of the shell at launch and 5.4 s after the launch is given by :

So, the speed of the shell at launch and 5.4 s after the launch is 13.38 m/s it is moving towards the Earth.