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Mass and Weight

 

  • What are the differences between mass and weight?
  • Mankind has only recently begun to develop and understand thermodynamics, the mechanics of motion science and its extension to temperature. We still have a lot of weight, mass, power, power, power, heat, heat, mix. Since weightlessness evokes space and space is beyond the atmosphere, we think that as soon as we get out of the atmosphere, our weight will disappear. Underneath all these confusions and misunderstandings lies the fact that some basic concepts and their relations with each other are not known correctly and intimately. Come, first look at these basic concepts.

 

    Mass weight

    Mass and weight

  • Mass
  • An iron piece called “a kilo“, used when weighing something on the balance, sometimes benefits other things like: nail lining, walnut breaking. Whether in tartar or other work, what is being utilized is an unchanging feature of the iron piece, like its name: Mass. The reason why it is called “one kilo” is that the mass is 1 kilogram or 1000 grams (1 kg = 1000 g). Wherever we are on earth, even on what satellite or planet we find, what turns around, how fast or slow we go, the mass of a “kilo” we carry will always stay at 1 kg and we will always work at the same level of work using kinetic energy such as nail lighter. It will work.

 

  • Mass is the constant identity of a substance. The protection of the material is equivalent to the change of mass. In the meantime, we are expecting that we will not change the mass as a substance, for example, weighing 72 kg, but the creatures change their masses due to the environment and nutrition and waste exchange needed to survive, the names we give to these changes, such as growth, weight loss, Every material, whether small or large, has its own mass. So we can call mass instead of substance.

 

  • Once we knew the mass, it was expected that we would not go into the concept of weight, which was most mixed with it. Although weight is a phenomenon that can be defined without gravity, since it is almost always perceived to be related to gravity, it is appropriate to first focus on gravity, more generally, mass gravity.

 

  • What is massive attraction?
  • The materials attract each other. That is, a substance applies a force to another, which forces it to come toward itself; It does so without the need for any linkage between them, such as springs, strings, air. The other matter likewise attracts the first one with a force of the same magnitude (and of course the reverse direction), which forces it to go towards itself. For example, while the Earth pulls down a tennis ball with a downward force, the tennis ball pulls the Earth upward with a force of the same magnitude. These equivalent pulling forces are directly proportional to the masses of the two materials. Again, this force is proportional to the virtual size of the two masses, as if they “saw” each other. For example, if a tennis ball 1 meter away is 2 meters away, it looks like a quarter of the old one is faded. We can not see the ball if it is 100 m away, that is, a small one in ten. The gravitational force also varies inversely with the square of the distance. So the tennis ball 1 meter away, the force we draw from the mass, falls 100 m away in ten minutes. But the force between us and the ball is so small that it will soon be so small that the ball will not patronize us in any direction. However, if none of the masses are too large, the gravitational force reaches a significant magnitude. For example, if we take the Earth to our place, its gravitational force (that is, the gravitational force acting on the ball) is so great that it prefers to approach (fall) the Earth as soon as the ball.

 

  • The distance that determines gravitational force is the distance between two objects centers of mass. If we take the ball on the earth and above, this distance is slightly different from the average radius of the Earth (6371 km). For him, being at sea level or higher, in equatorial or polar, does not change much, the gravitational force applied by the Earth. Approximately 1 kg mass impacts this average distance of 9,83 N (Newton). According to my rationale, in Istanbul, for example, if I was towed to 700 N, I would be subjected to an attraction of 5 N more on the Antarctic coast, 2 N less on the Everest peak. So far away? 650 N above ground (at any satellite distance), 22 N at 36 000 km (at ground station distance), 0.19 N at Moon distance; A declining force at the height of the distance, but still not zero. If we take other large masses instead of the Earth, for example, 115 N on the moon surface, 1/6 of the Earth, 0,4 in Merih (Mars), 2,7 in Customer (Jupiter), 28 in the Sun. On a typical neutron star, I would be pulled 1012 times more strongly than Earth; Because a mass as large as the Sun would have been close to the radius of the neutron star only a few kilometers. However, the difference in gravitational pull between my feet and my head will be so great that I will have become a regret long before I reach the star.
  • As long as you do not leave much of the world, the attraction of these masses is negligible. For example, the Moon can only shoot me now at 0.0023 N and the Sun at 0.41 N. Nevertheless, these little forces are the main cause of tidal events.

 

  • Noticeably, we never resorted to weight when talking about gravity. There is an important and gentle relationship between gravitational force and static weight; We will see in the future. A final word before moving to weight: The force of mass gravity is an unchanging magnitude as long as the distance between the objects remains the same. So as long as I’m at a height of 240 km, the gravitational force that will affect me will always be 650 N; Whether I’m standing there, or moving in a circular orbit, I’ll be shooting with 650 N all the time.

 

  • Weight
  • Weight and mass are two different concepts that are often mixed with each other or used interchangeably. The weight is actually measured in units of force. In practice, “weighing” with a comparator called the scale is known as a resultant size, but this is wrong. In fact, a simple, equal-arm balance compares the masses placed on two baffles. If the arm is able to stabilize in the horizontal position, it will balance the forces acting on it. For this, the masses must be equal. The mass of the potato, which is then balanced with “one kilo”, is 1 kg. What about weight? Weight can not be assigned with this kind of scale. This is the first confusion between mass and weight. Weighing the result of the weighing “the weight of the potato is a kilo”. However, it is necessary to say that “the weight of the potato is equal to the weight of a kilo”, we do not know either yet. This error went into our everyday purchases, our bath scales. Until recently, mass and its weight have been tried to be shown on the same scale, but even if names such as one kg-mass other than kg-force were given, the mechanics did not get rid of the nightmare. Still no one (including physicists) says “I am taking 700 Newtons” when speaking to you of weight; He says “72 kilos.” “Who is this 72 kilo?”, No one can answer the question, “My mass“, if you like.

 

  • As long as these mistakes remain only in our language and do not affect our understanding, there is no harm. In any case, the weight does not change much unless we are separated from the world too much; Speak weight weight. But we need to be more careful because the subject is weightless. Because there is no other way to know clearly what is the mass, what gravity or gravity of what is said to be weightless.

 

  • We have seen that mass has never changed, and the force of attraction has not changed as long as the distance between masses remains the same. We also know that as the distance increases, the force of attraction decreases rapidly, but it is never zero. There are other things we know based on experience. Under the so-called “weightless” conditions, for example, in an artificial satellite capsule (or in a rope-free elevator cab), we can protect our situation against the capsule without touching it at all; If we leave the tool we use as if we are left in the place we left. If we think carefully, it is like being “weightless” and not being exposed to any force except the gravitational force that we know we can never get rid of its effect. I mean, just and only if we are beneath the force of mass gravity, whether it is standing or not) we will not be moving, we will not have any weight. For example, when jumping on the trampoline to the pool, we are under gravity only until we are touched the first time that our feet abandon the trampoline, without any support from the ground (neglecting air rubbing). It ascends first, stops for a moment at a point, then drops down as we go down. In the meantime, there is no other force to make us feel that we are a weight. However, while we are standing (or sitting), each of our parts is compensated by pushing up with a certain force to prevent it from falling due to gravity. We perceive these forces as wholesale weight: with the most of our feet, at least with our heads (when we stand on the hill most of us, with our feet at least).

 

  • If we go up or down the elevator, we change our weight. We do not go into the cabinet and press the exit button to the press. Gravity balances (almost) with the force that pushes our feet upward from the floor, and we perceive this thrust as our normal weight. As we press the button, the floor accelerates by pushing us up with a bigger force, which makes us feel more heavy. When we take the fixed speed of the cabin, our weight returns to normal again. As we roll closer, the cab slows down, the treadmill diminishes, we feel a bit lighter (like in a little space). After stopping, everything returns to normal. The descent is repeated in the opposite direction: first, then normal, then weight, and finally return to normal. It is now clear what we will feel in a rapidly accelerating or deteriorating cabinet. The weight is more weight in the first, almost zero weight in the second.

 

 

 

 

 

  • It is also possible to analyze the situation within the shuttle-satellite. Shuttle, personnel, test equipment and Dr. Nurcan Baç’s zeolites (see Science and Technique 345, pp. 8-11), all move on almost the same orbit, if they want to touch each other, ie under gravity. There is no weight because no other force is needed; As well as a very long time. Thus, the zeolite crystals can grow in the most free environment. On the Earth, we would only be able to create a weightless situation for a few seconds, in a fall tower, to throw the cabin up and down again.

 

  • Gravity Acceleration
  • Newton’s famous second law of motion states that when a mass acts on a force, it accelerates in the direction of this force in proportion to the magnitude of the force, but inversely proportional to its mass (that is, its current velocity over time). It is this inverse proportion that mass is the measure of a property called “attribution” (laziness). You can easily accelerate a hand-held car. But with the same force it takes a long time to provide it in our car; Because your car is much more “inferior” or massive. Acceleration is “acceleration” in the mechanical language. After you leave the tennis ball away, if you ignore air resistance, gravity is the only force that acts on it, and it is straight down. When we leave zero, the speed increases by 9.8 meters per second, and the ball accelerates as it goes down. If the air resistance is not really there (for example in a fully ventilated room) the tennis ball, bird feather and millstone always accelerate with the same acceleration; Because the acceleration acting on the unit mass remains the same, for all objects. The force of gravity acting on this unit mass is called gravitational acceleration. It can be assumed that the application site is mostly the Earth’s surface, and as long as it remains there, it does not change much so it is a fixed average value. Go = 9.83 N / lk = 9.83 (m / s) / s = 9.83 m / s2.

 

  • On the other hand, when a objects movement is examined, it is often desired that this movement be defined according to the Earth. In such a case, the gravitational acceleration which regulates the absolute motion (that is, the movement according to a reference which can be regarded as a constant in space) is not a gravitational acceleration but a gravitational acceleration which will give motion according to the Earth becomes a more appropriate size. Its standard value is g = 9.81 m / s2. The altitude and latitude effects that give rise to differences from this are often neglected. The corrections that can come from the reasons such as the world not being symmetrical and changing the shape over time are much smaller.

 

  • Rapid movements require acceleration in a short time, that is, high acceleration. High acceleration in in-atmosphere and beyond motion programs is also expressed by accepting g as unit with m / s2 unit. For example, when a suit is launched, acceleration of 2-3 g accelerations in aircraft maneuvers will reach 2-3 times the weight, while accelerations like 8-10 g reach the limit of man’s endurance. Collisions are often measured with much higher G ‘s. For example, in tenis, the time of the ball to the racquet is 1/100 second and the ball exit speed is 50 m / s, the average acceleration will be 500 g.

 

  • In the unweighted cases, the acceleration based on the weight must also be zero, ie 0 g. So why microgravity? Factors such as weight, surface tension, electrostatic forces must be known in detail in processes involving phenomena such as natural convection, stratification, where the weight affects (and therefore need weightlessness). In a space station, the value of gravity is different from zero due to the fact that the gravity of the space is “under” and “above” the cabin, the movement of the staff, the rotation of the station or the exact trajectory of the theoretical gauge is non-zero and its boundaries must be known. Minor values ​​that can be reached can be between 10-5 g on a fall tower, 10-3 g on an airplane flying in a ballistic orbit, 10-6 g on a space shuttle (staff sleeping) and 10-3 g (running).

 

  • How to Measure?
  • Let’s take the mass first. Everything measured by mass is not weight or gravity, but mass is important. We can determine an unknown mass, for example by comparing it with a standard mass of 1 kg. Scale with arms, weighbridge, etc are for this job. In fact, since the comparison is between gravitational forces acting on known and unknown masses, it is possible to measure everything where the weight is large enough to operate the balance: in the poles, at the Everest, in the ascending or descending elevator. But we need to resort to other means so that there will be no weight in the satellite, or rather it will not be big enough. For example, we connect masses we do not know to a pedestrian we know and vibrate and compare the period to the period that a known mass will give.

 

  • The lever scale we use for mass measurement is useless for weighing. However, a springy balance can be safely used, provided that it is flat. Since the spring elastic elongation characteristics are the same everywhere, we weighed a standard weight of 1 kg, weighing 9,78 N in Singapore, 9,80 N in Ankara, 9,83 N in the North Pole, Or mild, and we might lose weight on a satellite in orbit.
  • Back to remember how we define weight. In fact, during weighing with a spring scale, we apply an additional force on the spring extension, other than gravity, gravity, and we read this weight, which we have defined as weight, with the spring extension amount and read it from the scale scale. So everything is consistent. (Perhaps the only reason for the weight to lose weight instead of Newton, but it is easy to turn it to Newton by multiplying it by 9.81 N / kg.)

 

  • How are we going to measure gravity? The classical balance still has no use. The spring balance, together with the mass we hold, must keep the gravity constant at the point where we will be measuring. Even if the distance from the world is fixed, there is no turning back to an orbit or any other movement. Because the spring force measured by the forces required by these movements can not only give gravity. It is almost impossible to measure by standing in a place. An exception may be measuring gravity, perhaps because there is no movement in the pole (except the motion around the Sun) that occurs as the Earth turns. However, in the ecovord, a body that rotates with the Earth must act upon a straight line, a force that allows it to stay on the Earth at any moment. That force is the difference between gravity and weight. We can then find gravity by adding this force to the weight we can easily measure. The fact that the difference is small makes it easy to ignore it. On the other hand, the weight supports the widespread misidentification of gravity. We have heard so many people that you are free from gravity in the space lab. However, we know that even there, if the Earth was attracting us with 650 N, we could carry out an unweighted “space walk“.

 

  • In fact, there are no places where we can really get rid of gravity. For example, if you approach the Moon from the Earth to the Moon so close to 1/9 (42 to 600 km from the Moon), the two will destroy each other because their gravitational forces are on equal and opposite sides, and only you and the other celestial objects will affect the gravitational force. It is impossible for all gravitational forces to destroy each other.

 

  • Will it weigh without gravity?
  • Although we find some relationships between gravity and gravity, weight is a form of detection that can be created without gravity. If you are making an accelerated journey in the above mentioned dead point between Earth and Moon, if you do not have gravity, you will perceive a weight proportional to acceleration and mass. You can stick to the wall in a cylinder rotating rapidly around the vertical axis and stand still. You give other examples.

 

  • Finally, let’s talk about the centrifugal force. Nedense, we are very much fond of the third law of Newton, known as “Impact = Reaction (or Action).” So much so that we do not hesitate to use it even in socially and more complex areas. In fact, although the above-mentioned basic second law is a special application, it is known in a much more common environment. According to this, if I weight is pushed up from the ground with equal force, I push the ground downward with a force of the same magnitude. If you push a stone by eliminating it, it pushes it back with the same force. If the world is pulling me down 700 N, I will pull the Earth up to 700 N force. It’s a discovery world. These are not important. But when things start turning, things get mixed up. Think of a ring attached to a thin rope tip. The rope is fixed at the other end; The ring is spinning fast on a horizontal circle stretching the rope tightly. Let’s forget the Earth, gravity, weight, air to make the job easier. Impact and reaction forces, which have not been seen in previous examples, are now stretched. I will continue with a dialogue after this.

 

  • Curious (C) – An impulsive force must be stalling!
  • Smarty-Pants (S) – No two forces.
  • C- Two? Where are these?
  • S- The pin is on both sides.
  • C- Haa, I understand. The forces must be equal; I already said a force for him.
  • S- Yes, equal. Because if one were bigger than the other, the rope would flee rapidly toward the direction of great force, while it stood in place.
  • C- How beautiful, I think Impact = We got the reaction.
  • S-!
  • C- Who is applying the forces?
  • S- Reliable nail at the fixed end.
  • C- At the other end?
  • S- Of course, the ring and the rope are stretched outward (from the center of the circle) and called centrifugal force in it.
  • C- The ring? Who is applying to him or what?
  • S- İp .. According to the Principle, the centrifugal force that the ring applies to itself is equal and opposite, and the centripetal force for it.
  • C- Anything else?
  • S- No one else, no others.
  • C- Would that be? Where is our principle?
  • S- How quickly did you forget; We introduced it as a special case of the second law.
  • C- What is that special case?
  • Q- In the absence of mass: By isolating the “touch” or “met” of the effect and reaction from all the surrounding objects, there remains something “empty” or zero mass. I mean nothing. Zero mass must have zero force in order for it to stay there, or else it will run away with infinite acceleration. Zero force, however, is bound by your Principle, ie Impact – Response = 0.
  • C- What will you say about the rope? Impact and reaction to the meeting place ip; But the rope is “nothing”.
  • S- Actually, you are right, but the rope is very thin so mass is almost zero. Have you ever felt that you were applying a force to move the rope to the left or right while it was idle? A challenge?
  • C- No, I can not test it … Now I understand why, between the nails and the ring ends Impact = We can say the reaction. In fact, “almost” should be added.
  • Thus, in general, an equal and opposite force or an opposite force does not have to act on an object. Then the object moves. The only force on the ring is the pulling force in the direction of the rope nail.
  • C- But then the ring will be accelerated by the second blood. However, it is enjoyable at constant speed.
  • S- It is not wrong, but this time you are missing the second law. Acceleration and acceleration are not about increasing speed on the road. Remember that if the force is influential in the direction, the new speeds are won in that direction. What happens when a ball rolls on a straight road and winds sideways?
  • C- Of course the speed of the ball on the road does not change, but the ball approaches the edge of the road.
  • S- So it gains speed to the side. Here the ring te continues to spin at constant speed, because the rope pulls it in side (inside).
  • C- I understand, but then the ring should go to the nail as the ball goes sideways?
  • So you think it does not work?
  • C- Of course not; I’m always nervous.
  • S- No, it’s gone. If he was not going to pull it, what would he do?
  • C- I do not know.
  • Sid you try cutting the dice?
  • C- Really, I’m going to grab a rope with my new laser lighter, see what happens. (Sener, the rope breaks, and the ring leaves everything and flings along a straight line.)
  • S- What happened?
  • C- It’s getting away from the crowd and all of us. I wish I had not, ipi. Even though it seems that the moon does not seem to go away, at any moment it seems to remember the nail and bend towards it.
  • S- Well, it is also in the suites .. The world has assumed the role of nail, and sat on the satellite. There is no rope, rope, or object that you can burn, you can tear. Of course, there is no need for centrifugal force to stretch them. But centripetal force, that is, gravity is everywhere.
  • C- But I, I believe that centrifugal force very much. It’s relieving me that the centrifugal force is something that returns.
  • S- I understand, but you can always do it. First find the real force needed for motion (like gravity). Then turn it over and give it whatever you name it. It turns out to be centrifugal, if not anything else. S’Alembert has already done this. It was probably Impact = Response enthusiast. It is possible to interpret the law of motion as Force + Inertia Force = 0, when the real force is the inverse of the multiplication of the mass with the force equal to it, ie, by changing its sign or direction, and giving it the name ” It’s like a static force balance condition.
  • C- Is this necessary?
  • S- No, it’s a matter of taste, habit, vision. The important thing is to apply it correctly, know its limits. It’s like everything.
  • C- Thank you.
  • Come back.

 

Mass and Weight
Author: wik Date: 12:21 am
Science and Mathematics


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