What is weightlessness? How does weightlessness arise in various situation? Give some problems of weightlessness.

Weightlessness:
When a body presses against a supporting surface, the surface exerts a reaction force, creating the feeling of weight. If this reaction force becomes zero, the apparent weight of the body also becomes zero. A body is said to be in a state of weightlessness when the reaction force from the supporting surface is zero or its apparent weight is zero.

A body can experience weightlessness in the following circumstances:

1. In a Freely Falling Lift:
Consider a person with true weight standing in a lift moving vertically downward with acceleration. The reaction force of the floor on the person reduces as the lift accelerates downward. If the lift’s cable breaks and it begins to fall freely, both the person and the lift move downward with the same acceleration, and there are no forces of action and reaction between them. In this case, the person experiences weightlessness.

2. Inside a Spacecraft:
A spacecraft orbiting Earth experiences gravitational pull, and a body inside the spacecraft also feels the pull of gravity. However, both the spacecraft and the body inside it are in free fall, orbiting the Earth. This results in the body inside the spacecraft experiencing weightlessness, as there is no reaction force acting on it.

3. At Null Points in Space:
In certain points in space, called “null points,” the gravitational forces from different celestial bodies cancel each other out. At these points, the gravitational acceleration is zero, resulting in zero effective weight.

4. At the Centre of the Earth:
At the Earth’s center, gravity cancels out in all directions, so the value of gravity is zero, meaning the weight of a body is also zero at that point.

Problems of Weightlessness:
1. Eating and Drinking:
In weightlessness, eating and drinking become difficult. An astronaut cannot drink water from a glass, as the water would float out in drops. Food is consumed in paste form, squeezed from a tube.

2. Adverse Effects on the Human Body:
Extended spaceflight in a weightless environment can negatively affect the human body, leading to muscle atrophy and bone density loss.

3. Movement in a Spacecraft:
While moving in a spacecraft, astronauts may be pushed away from the floor and might collide with the ceiling due to the absence of gravity.