Why Does Weightlessness Occur?
Weightlessness is the absence of sensation of the weight. The weight of an object is defined as the product of the mass and acceleration due to gravity. While studying gravitation, we come across many interesting facts about the effects of gravity, one among them being zero gravity or weightlessness. We know that the weight of an object is the force with which the earth attracts the object. When a person standing on the surface of the earth he/she will be experiencing the weight, earth will exert a force equal and opposite to the weight of the person. In this article, we will come across a detailed understanding of the weight and weightlessness of the object.
What is Weightlessness?
To understand what weightlessness is, we must begin with the effects of gravity and the concept of weight. From the definition of weight, we know that weight is directly proportional to the mass of the object. As the mass of the object increases the weight of the object will also increase. Now, the question that arose after the definition of weight, what is weightlessness?
Weightlessness is encountered when the object undergoes free fall. When a person standing on the surface of the earth he/she will be experiencing the weight, earth will exert a force equal and opposite to the weight of the person to keep him at rest. The same principle holds good when we measure the weight of an object by spring balance hung from a fixed balance. The object will fall unless there is an external force acting on it in the opposite direction of gravity. Now, let us imagine both ends of the spring balance are free, both springs will move concerning acceleration due to gravity, then the object will feel zero gravity. This phenomenon of freefall is known as weightlessness.
Now, let us have a look at the weightlessness definition. So, weightlessness is the phenomenon of zero gravity when an object or a person experiences freefall. In other words, Weightlessness is a condition experienced while in free fall, in which the effect of gravity is cancelled by the inertial (for example, centrifugal force) force resulting from the orbital flight. It is also known as zero gravity and it is often used to describe such a condition i.e., Freefall, where the only acceleration offered is the acceleration due to gravity.
Astronauts who are working to orbit the Earth get the weightlessness experience or its sensation often. Orbiting astronauts experience a similar experience of such sensations just like the people who feel at the time of leaving a seat in an amusement park. The sensations are the same for both riders and astronauts but the causes behind weightlessness are also the same. But, there are a few people who find it difficult to comprehend the weightlessness concept.
Weightlessness in the Orbit
You think that an astronaut in the orbit station remains weightless as:
No gravity is available in space and these astronauts do not have a weight at that time. Space itself is known as a vacuum and we all know that vacuum does not contain gravity. The astronauts go farther from the Earth and this is a location that has a minimal effect on gravitation.
If you are also a believer in such statements, then you will take a bit of time to remap and rearrange your thoughts to comprehend the true cause behind the weightlessness. This is the first rule of Physics that some unlearning is crucial before you go for real learning. Here are the two competing ideas that take you to the correct definition by removing preoccupied notions from your mind.
Contact Vs Non-contact Forces
There are two prime categories known as distance and contact forces. Once you sit on the chair, these two forces can be experienced. Earth’s gravitational force will pull you down and the gravitational force of the chair will pull you upward, this is due to the contact between the bottom end and top of the chair. This is defined as a contact force that is the outcome of the real touch of two interacting objects (you and the chair). The non-contact force here is the Earth that works on exerting mass mutual pulling as Earth and you are not in physical contact.
Weight and Scale Reading
Vedantu helps you comprehend it as per the technical aspect. We all know that scale is not able to measure our weight but we use a scale for the measurement of weight. Here, it has to be noted that reading via scale is an actual measurement of the upward force that is applied via a scale for balancing the downward gravitational force as per an object's action. When this object comes in an equilibrium state in motion or stable in constant speed, then these two forces get balanced. The upward force equalizes the downward scaling according to the weight of a person. When you are standing on the scale and bouncing up and down, then the reading scale may go through a fast change.
Weightlessness in Space
Astronauts orbiting in space feel a way of weightlessness because there's no external contact force in space pushing or pulling upon their bodies. Gravity is the only force acting upon their body. Gravity being an action-at-a-distance force can't be felt and thus wouldn't provide any sensation of weight. Thus astronauts feel weightlessness in space.
Crews of spacecraft are subject to the issues of weightlessness. It was learned from early Soviet and U.S. manned missions that there's a decrease in heart and respiration rates and a progressive loss of weight and bone calcium during flights of relatively short duration. A reversal of most of those effects occurs, however, upon return to Earth. On later missions of extended duration, like those involving the U.S. Skylab and Soviet Salyut space stations, extensive biomedical studies were undertaken.
The sensation of weightlessness, or zero gravity, happens when the effects of gravity are not felt but can be experienced. In general, gravity does exist everywhere in the universe because it is defined as the force that attracts two bodies to each other. But astronauts in space usually don't feel its effects.
The ISS (International Space Station), for example, is in perpetual freefall above the Earth. Its progress, however, almost equals the speed of its fall toward the earth. This means that the astronauts inside aren't pulled in any particular direction. So they float.
Not having in touch weight on your feet sounds relaxing, but within the future, there are many health problems related to it. Bones and muscles weaken, and other changes also happen within the body. One of the functions of the ISS is to study how astronaut health is affected by long periods of weightlessness.
Examples of Weightlessness
Let us have a look at some examples of weightlessness. Other than falling from the top, objects attached to a spring with free ends, etc. Other than these, there are many examples that elaborate weightlessness.
Astronauts in the spaceship will experience weightlessness almost, we witness them floating due to zero gravity.
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People using elevators will experience weightlessness or zero gravity. The weightlessness experienced in the elevators is known as effective weightlessness. This is the best explanation for the weightlessness that elaborates weightlessness doesn’t mean the absence of gravity but it means the absence of sensation of the gravity or weight of the object. Also, this can explain that mass and weight aren’t the same factors, though a person is feeling weightless that doesn’t mean they are massless.
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Did You Know?
Weightlessness doesn’t make people weightless. People aren’t weightless on the ISS (International Space Station). 90% of the Earth’s gravity still affects the ISS (International Space Station), so people weigh 90% of what they would on Earth. The reason the astronauts float is that the ISS is in perpetual free-fall around the Earth, an orbit in which microgravity takes effect because the people and objects inside fall at the same rate as the ISS itself.
Conclusion
So, you must have comprehended the topic of weightlessness fully by now. If you still have a few queries in your mind, then you are free to discuss them with the Vedantu experts. When you find something challenging while doing self-study, then you can make a list.
FAQs on Understanding Weightlessness in Physics
1. What is the principle of weightlessness in Physics?
Weightlessness is the state in which a body does not experience the sensation of weight. It is not the absence of gravity, but the absence of a contact force (like a floor or a chair) pushing back against the body. This condition is primarily achieved when a body is in a state of free fall, where gravity is the only significant force acting upon it. The body and its surroundings accelerate downwards at the same rate, so no internal stress or sensation of apparent weight is felt.
2. Does weightlessness mean there is zero gravity?
No, this is a common misconception. Weightlessness does not mean zero gravity. Gravity is very much present in most situations where weightlessness is experienced, such as in an orbiting space station. For example, at the altitude of the International Space Station (ISS), Earth's gravity is still about 90% as strong as it is on the surface. Weightlessness occurs because the astronaut and the station are in a constant state of free fall around the Earth, accelerating at the same rate due to gravity. Since no surface is pushing up on the astronaut, they feel no apparent weight.
3. What are some common examples of weightlessness?
You can experience weightlessness in several situations, even on Earth. Common examples include:
- Astronauts in Orbit: An astronaut floating inside an orbiting spacecraft is the most famous example of sustained weightlessness.
- A Freely Falling Elevator: If the cable of an elevator were to snap, a person inside would be in free fall and would feel weightless.
- Amusement Park Rides: The brief sensation of floating you feel at the apex of a steep drop on a roller coaster is a moment of near-weightlessness.
- Parabolic Flights: Special aircraft flying in a parabolic arc can create short periods of weightlessness, which are used for astronaut training.
4. How is weightlessness represented by a formula?
Weightlessness can be understood using the formula for apparent weight. The apparent weight (R) is the normal reaction force experienced by a body. The formula is R = m(g - a), where 'm' is mass, 'g' is acceleration due to gravity, and 'a' is the downward acceleration of the reference frame (like a lift). A body experiences true weightlessness when its apparent weight (R) is zero. This happens when the downward acceleration 'a' equals the acceleration due to gravity 'g', making the equation R = m(g - g) = 0.
5. Why do astronauts feel weightless in an orbiting space station?
Astronauts feel weightless because both they and their space station are in a continuous state of free fall around the Earth. The space station doesn't simply float; it is constantly falling towards Earth. However, it also has a very high horizontal velocity, which causes it to continuously "miss" the Earth, resulting in a stable orbit. Since the astronaut and everything inside the station are falling together at the same rate, there is no contact force between them and the station's surfaces. This lack of a normal reaction force creates the sensation of weightlessness.
6. What are the necessary conditions for a body to experience weightlessness?
The primary condition for a body to experience weightlessness is that the net non-gravitational force acting on it must be zero. This means the apparent weight of the body is zero. This state is achieved when a body is undergoing free fall, where it accelerates solely under the influence of gravity. In this situation, the body's frame of reference (like a falling lift or an orbiting satellite) accelerates downwards at the same rate as the body itself (a = g), so no supporting or contact forces are exerted on the body.
7. What is the difference between mass and weight, and how does it relate to weightlessness?
Understanding the distinction between mass and weight is crucial to understanding weightlessness.
- Mass is the amount of matter in an object, an intrinsic property measured in kilograms (kg). It remains constant regardless of location.
- Weight is the force of gravity acting on an object's mass (W = m × g), measured in Newtons (N). It changes depending on the gravitational field strength.
8. How does prolonged weightlessness affect the human body?
Prolonged exposure to weightlessness has significant physiological effects because the human body is adapted to Earth's gravity. Key examples include:
- Bone Density Loss: Without the constant stress of supporting the body's weight, bones begin to lose calcium and density.
- Muscle Atrophy: Key postural muscles in the legs and back weaken and shrink because they are no longer needed to work against gravity.
- Fluid Shift: Bodily fluids redistribute from the lower body to the upper body and head, causing a puffy face and sinus congestion.
- Cardiovascular Changes: The heart does not have to work as hard to pump blood, which can lead to a decrease in its size and overall conditioning over time.
