how can you explain free-fall?

Answer 1

Free-fall requires that the gravitational pull of the earth is the only force driving the object toward the ground. In reality, air causes some friction but it's small and often ignored.

Free-fall can be explained by Newton's third law
F=ma.
In the case of free-fall, F is the gravitational pull, and is approximately constant over time. m is the mass of the object and is constant. This means acceleration a is constant. As a result, the speed at which the object falls increases proportional to the time it's been in its fall, and the proportional factor is exactly a. Also, because the falling speed keeps increasing, the distance the object travels exhibits a parabolic curve.

To understand free-fall, it helps to review Newton laws. Just think of gravity as a constant force exerted on an object.

Answer 2

Free fall is motion with no acceleration other than that provided by gravity. This also applies to objects in orbit even though these objects are not falling in the usual sense of the word. Strictly speaking nothing falling through an atmosphere can be in free fall due to the inherent resistance to motion, however in skydiving, the term is also applied to the period of the jump before the parachute is opened, and in colloquial usage, falling through an atmosphere is normally considered to be free fall.

Examples of objects in free fall include:

* A spacecraft with its rockets off in space.
* The Moon orbiting around the Earth.
* An object dropped in a vacuum tube
o for a physics demonstration
o at NASA's Zero-G Research Facility

Examples of objects not in free fall:

* Standing on the ground, as the gravitational acceleration is counteracted by the reaction force from the ground.
* Flying horizontally in a plane, as the wings' lift is also providing an acceleration.
* Jumping from a plane, as there is a resistance force provided by the atmosphere.

Answer 3

Free fall is motion with no acceleration other than that provided by gravity. This also applies to objects in orbit even though these objects are not falling in the usual sense of the word. Strictly speaking nothing falling through an atmosphere can be in free fall due to the inherent resistance to motion, however in skydiving, the term is also applied to the period of the jump before the parachute is opened, and in colloquial usage, falling through an atmosphere is normally considered to be free fall.

Examples of objects in free fall include:

A spacecraft with its rockets off in space.
The Moon orbiting around the Earth.
An object dropped in a vacuum tube
for a physics demonstration
at NASA's Zero-G Research Facility

Answer 4

Free falling bodies experience no acceleration in their own frame because of the weak equivalence principle which says that the mass constant in F=m*a is the same as the mass in the formula for the gravitational force: F=G*m*M/r^2. If one equates the two

m*a=G*m*M/r^2

and independent of the composition of the falling body. One can then eliminate the mass of the body in free fall:

a = G*M/r^2

General relativity would not be possible if this wasn't the case.

Einstein illustrated that with his falling elevator car Gedanken-experiment: a person in a falling elevator car can not tell if the car is being accelerated in a gravitational field or not because they will follow exactly the same trajectory as the car and there will be no measurable forces. Of course this only holds strictly for a homogeneous field or in an infinitesimal volume element, but the differential form of Einstein's Equations takes care of that.

Answer 5

There's not much to explain. You're in an accelerating frame of reference with no opposing force. It's pretty simple.

Doug

Answer 6

falling to the earth before hitting the ground.

Answer 7

falling freely!

Answer 8

complex thing query from google or bing that might help