Answer:
When a body starts a free fall motion towards the planet earth's surface or the ground it is under the free fall motion, which means that there is a net force,F(gravity) applied on it by the planet. Now, there will be also the mass,m of the object which will tend to move much faster towards the earth. But, a point will come when the total amount of tension due to the moment of the object balances with the gravitational pull of the planet.As, there is a net constant speed attained by the object in moving towards the surface of the planet.
- <u>The air resistance,R(due air):</u>
The gravitational force and the tension presented by the motion equals,as the motion becomes more constant in nature covering each point in equal intervals of time. Because, the upthrust force becomes equal to the downward force presented by the object itself.
Upthrust force= Downward force.
- <u>Acceleration during free fall motion:</u>
The value of acceleration,a will be same for each and every object moving towards the planet with a terminal velocity,Vt. As, it will be 9.8 m/sec² which is supposed for each object, irrespective of its properties and size.
Example: When paratrooper jumps from a plane, at first he is moving with the increasing speed and velocity but when he reaches a point or level where the upthrust force provided by the drag and the downward force due to the gravity of planet levels, the body attains the acceleration value around 9.8 m/sec².