It explained how high tides and low tides are formed due to gravitational force of the moon and the Sun on the surface of water. On signing up you are confirming that you have read and agree to Terms of Service. What is the importance of universal law of gravitation? Answer Universal law is important because it explained several phenomena which were believed to be unconnected. The Sun also affects tides, although it has about half the effect of the Moon.
However, the largest tides, called spring tides, occur when Earth, the Moon, and the Sun are aligned. Figure 6. Note that this figure is not drawn to scale. Tides are not unique to Earth but occur in many astronomical systems. The most extreme tides occur where the gravitational force is the strongest and varies most rapidly, such as near black holes see Figure 7. A few likely candidates for black holes have been observed in our galaxy. These have masses greater than the Sun but have diameters only a few kilometers across.
The tidal forces near them are so great that they can actually tear matter from a companion star. Figure 7. A black hole is an object with such strong gravity that not even light can escape it. This black hole was created by the supernova of one star in a two-star system. The tidal forces created by the black hole are so great that it tears matter from the companion star. This matter is compressed and heated as it is sucked into the black hole, creating light and X-rays observable from Earth.
In contrast to the tremendous gravitational force near black holes is the apparent gravitational field experienced by astronauts orbiting Earth. Or what about the effect of weightlessness upon plant growth?
The term just means that the astronaut is in free-fall, accelerating with the acceleration due to gravity. If an elevator cable breaks, the passengers inside will be in free fall and will experience weightlessness. You can experience short periods of weightlessness in some rides in amusement parks.
Figure 8. Astronauts experiencing weightlessness on board the International Space Station. Microgravity refers to an environment in which the apparent net acceleration of a body is small compared with that produced by Earth at its surface.
Many interesting biology and physics topics have been studied over the past three decades in the presence of microgravity. Of immediate concern is the effect on astronauts of extended times in outer space, such as at the International Space Station. Researchers have observed that muscles will atrophy waste away in this environment. There is also a corresponding loss of bone mass. Study continues on cardiovascular adaptation to space flight.
On Earth, blood pressure is usually higher in the feet than in the head, because the higher column of blood exerts a downward force on it, due to gravity.
What difference does the absence of this pressure differential have upon the heart? Some findings in human physiology in space can be clinically important to the management of diseases back on Earth.
On a somewhat negative note, spaceflight is known to affect the human immune system, possibly making the crew members more vulnerable to infectious diseases. Experiments flown in space also have shown that some bacteria grow faster in microgravity than they do on Earth. However, on a positive note, studies indicate that microbial antibiotic production can increase by a factor of two in space-grown cultures.
One hopes to be able to understand these mechanisms so that similar successes can be achieved on the ground. In another area of physics space research, inorganic crystals and protein crystals have been grown in outer space that have much higher quality than any grown on Earth, so crystallography studies on their structure can yield much better results.
Plants have evolved with the stimulus of gravity and with gravity sensors. Roots grow downward and shoots grow upward. Plants might be able to provide a life support system for long duration space missions by regenerating the atmosphere, purifying water, and producing food.
Newton's law of universal gravitation is about the universality of gravity. Newton's place in the Gravity Hall of Fame is not due to his discovery of gravity, but rather due to his discovery that gravitation is universal.
ALL objects attract each other with a force of gravitational attraction. Gravity is universal. This force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance that separates their centers. Newton's conclusion about the magnitude of gravitational forces is summarized symbolically as.
Since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled.
If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on. Since gravitational force is inversely proportional to the square of the separation distance between the two interacting objects, more separation distance will result in weaker gravitational forces. So as two objects are separated from each other, the force of gravitational attraction between them also decreases. If the separation distance between two objects is doubled increased by a factor of 2 , then the force of gravitational attraction is decreased by a factor of 4 2 raised to the second power.
If the separation distance between any two objects is tripled increased by a factor of 3 , then the force of gravitational attraction is decreased by a factor of 9 3 raised to the second power. The proportionalities expressed by Newton's universal law of gravitation are represented graphically by the following illustration. Observe how the force of gravity is directly proportional to the product of the two masses and inversely proportional to the square of the distance of separation.
Another means of representing the proportionalities is to express the relationships in the form of an equation using a constant of proportionality. This equation is shown below.
The constant of proportionality G in the above equation is known as the universal gravitation constant. The precise value of G was determined experimentally by Henry Cavendish in the century after Newton's death.
This experiment will be discussed later in Lesson 3. The value of G is found to be. The units on G may seem rather odd; nonetheless they are sensible. Knowing the value of G allows us to calculate the force of gravitational attraction between any two objects of known mass and known separation distance. As a first example, consider the following problem.
The solution of the problem involves substituting known values of G 6. The solution is as follows:. This would place the student a distance of 6. Two general conceptual comments can be made about the results of the two sample calculations above.
First, observe that the force of gravity acting upon the student a. The predictions about the orbits and time period of the modern artificial satellites made on the basis of this law proved to be very accurate. The prediction about solar and lunar eclipses, made on the basis of this law came out to be very true. The gravitational force of earth ties the terrestrial objects to the earth. This law explains the attractive force between any two objects having a mass. The formation of tides in the ocean is due to the force of attraction between the moon and ocean water.
All planets make an elliptical revolution with the sun. The rotation of the earth around the sun. The rotation of the moon around the earth.
0コメント