## Note on Free fall and Weightlessness

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Freefall

If an object is falling freely under the action of gravity alone without any external resistance then the situation is called free fall.

During free fall an object falls with the acceleration which is equal to the acceleration due to gravity of that planet or satellite.

i.e. Acceleration of falling body = acceleration due to gravity during free fall. a = g

But if there is air resistance the situation of free fall does not arise. Thus, if there is no freefall then a < g

### Examples of free fall

1. The fall of an object on the moon where there is no air resistance
2. The fall of an object in the space where there is no effect of gravity.

The paratroopers land safely on the ground with the help of parachute:

It is because no free fall takes place if a person is falling with the help of a parachute. The parachute will increase the air resistance. Due to this, the acceleration of the falling parachute becomes less than the value of acceleration due to gravity. As a result, he or she could safely land on the ground.

In case of the moon:

One cannot land safely, because due to the absence of the atmosphere (air resistance). Hence, the parachute will fall freely on the moon. There is a high chance of getting hurt.

The probability of getting hurt is more when one falls from the significant height because:

The ground striking velocity while falling from a significant height will be more and, therefore, the effect of force also will be more. It is because momentum (M) will be more since,

Momentum = Mass x Final Velocity

i.e. p = m x V

### Weightlessness:

If the reaction that makes us conscious of our weight, when we stand or walk, becomes zero due to some reasons, one will feel weightless.  Weightlessness is the condition in which the weight of the body seems to be zero. A body with a fixed mass will be weightless under the following conditions:

1. When a body falls freely under the influence of the force of gravity only.
2. When the acceleration of a falling body is equal to the acceleration due to gravity.
3. When a body is at the center of the earth or in the space at null point (g = 0 → w = mg = 0)
4. The body in the artificial satellite or rocket becomes weightless while orbiting around a heavenly body.

1. If an object is falling freely under the action of gravity along without any external resistance then the situation is called free fall.
2. If there is atmosphere, there is no free fall because of air resistance.
3. Freefall is the situation of having zero weight of a body with certain mass and acquired when a body is in free fall or there is no gravity.
4. Weightlessness of a body is the state in which the body experiences that the body is not being attracted by any force.
5. Weightlessness occurs during free fall and at the null point.
6. The space between any two heavenly bodies at which the resultant gravity is zero is said to be a null point.
7. In a falling parachute, when a weight of the parachute becomes equal to the air resistance, its acceleration is zero.
.

### Very Short Questions

When there is no air resistance, a coin and a feather fall together. Acceleration of the feather and a coin at that instant is 9.8 m/s2. All objects fall towards the earth"s surface with the same acceleration despite the difference in masses if air resistance is not there. In reality, the objects with greater mass fall faster because they experience less air resistance. But, as the coin and feather do not experience any air resistance they have the same acceleration.

The free fall is defined as the falling of an object in absence of any external resistance with acceleration equal to the acceleration due to gravity.

Weightlessness is a condition when any object falls freely under the action of gravity experiencing no weight of its own.

On the earth the parachute at first falls with higher speed. But after certain time the upthrust of the earth and its downward force balance eachother. Due to balance forces it attains a constant velocity. But on the moon there is no atmosphere. Therefore, parachute falls down with acceleration due to gravity on the moon.

Air is always present in real life due to the obstruction of air objects do not fall freely.

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• ### Free fall does not takes place if a person is falling with the help of parachute, because it will ______.

increase the air resistance

not change the air resistance

none of the answers are correct

decrease the air resistance

• ### The probability of getting hurt is more when one falls from the significant height because ______.

The ground striking velocity while falling from a significant height will be less and therefore the effect of force also will be less

The ground striking velocity while falling from a significant height will be more and  the effect of force also will be less

The ground striking velocity while falling from a significant height will be less and therefore the effect of force also will be more

The ground striking velocity while falling from a significant height will be more and therefore the effect of force a will also be more

• ### Which of the following is the condition required for free fall?

There should be no gravity, if the body is at earth's center or at null point.
The object should not be in free fall

The object should not be beyond the gravitation field

The acceleration of a falling body should not be equal to the acceleration due to gravity.
• ### Why it is not safe to use parachute on the moon?

Because due to absence of gravity, parachute will fall-freely on the moon. There is high change of getting hurt.
Because the ground striking velocity while falling from a significant height will be more and therefore the effect of force also will be more.
Because due to absence of air resistance, parachute will fall-freely on the moon and there  is high chance of getting hurt.
None of above
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