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Answers to Readers' Questions on Physics: Gravity
The following 177 questions have been answered. They are listed according to date.
List of first 10 items
- Question regarding the "sign" of the velocity
- Gravity is the intrinsic force of magnetism
- Why don't we fly off the Earth?
- Which has the greatest force of gravity?
- Explain how gravity is the same for all objects
- Gravity is the side effect of molecular force
- What is your weight on the Moon?
- Is gravitational force an electrostatic force?
- Studying gravity and have some questions
- Want to calculate force between two iron balls
Question regarding the "sign" of the velocity
Question
October 7, 2009
I have a question regarding the "sign" of the velocity of an object when thrown upward.
When the object thrown upward, my math book says the velocity is positive, after reaching the highest point, the object starts going down, the direction of the velocity then negative. This seems to be opposite to your examples.
Thanks.
Kim - USA
18449
Answer
You have to be aware of the convention used in whatever book you use. Our logic is that when you drop an object, it is naturally increasing in speed. Thus, we called downward toward the ground as the positive direction for gravity. So, if you throw the object up, it is going in the opposite direction of gravity.
The most important thing is that your answer for the time, velocity and distance traveled is correct.
For your book's examples, use up as positive, but in our examples use up as negative. As long as you are consistent within an equation, the results should be the same.
Gravity is the intrinsic force of magnetism
Question
August 30, 2009
Gravity is the intrinsic force of magnetism, one lineral speed, and a variable of rotational speeds.
- USA
18235
Answer
I've never heard of any relationship between gravity and magnetism, especially since gravity affects non-magnetic matters too.
Why don't we fly off the Earth?
Question
August 21, 2009
If earth is revolving at very high speed then why should not we fall
YASHU SHARMA - India
18179
Answer
The rotates at only 1 revolution per day, which is very slow. Although there is some centrifugal force pulling us away from the ground, the gravity of the Earth is many times stronger, keeping us on the ground.
Which has the greatest force of gravity?
Question
June 29, 2009
Which one of the following objects will have the greatest force of gravity to the earth at its surface??.......
1) Alarge book
2)Ahouse
3)An average size car
4)A human bening
kaleem - KSA
17958
Answer
The force of gravity is greatest for the heaviest item.
Explain how gravity is the same for all objects
Question
June 12, 2009
If the acceleration of gravity is the same for all objects, how can you explain your results?
Leah - USA
17897
Answer
Try dropping two objects from the same height at the same time, you will see they hit the ground at the same time. Do not use a light object that is affected by air resistance. This type of experiment proves the rule.
Gravity is the side effect of molecular force
Question
May 18, 2009
Gravity is the side effect of the force that binds atoms/molecules together. This is one of the reasons it is a weak force, and a constant force, and also the reason why it cannot be identified as a separate force. It is also why, as one moves away from earth, the force of gravity diminishes arithmetically. Gravity does have an affect on light waves, speeding up light at the top of a wave if that light wave is within a certain distance of a sun or planet. This is one of the reasons light is a wave and a pulse. The 'speeded' up light moves into another dimension, and as the speed diminishes over time, it returns to our universe as DARK MATTER.
Want to learn more.... contact me.
Jacob - Canada
17765
Answer
Thanks for your theories on gravity. It is subject that has puzzled scientists and has resulted in a number of theories.
One theory of forces is that the exchange of gluons binds atoms together, while graviton particles are responsible for gravity. Gluons exhibit a strong force and gravitons represent a weak force. As far as I know, the theory does not say that gravity is a side-effect of molecular forces.
It is true that gravity affects light. The Theory of Relativity states that space curves near matter, causing they effect of gravity. But Quantum Mechanics shows that light particles--photons--can behave as matter. In either case, the effect of gravity on light has bee experimentally demonstrated.
What is your weight on the Moon?
Question
March 21, 2009
i had a question on my text book that-
"Your mass on the earth is 42 kg. What will be your weight on the moon? (g on moon = 1/6 X g, on the surface of the earth."
when i am writing the solution, like-
W=mg (on earth)
and W=mg1 (on the moon)
here i had problem, that what shall i write,
W=mg1 or W=mg.
If you would kindly clarify this problem!!!!!!!!!
Mahir - Bangladesh
17483
Answer
Mass is the same on both the Moon and Earth. Mass is how much matter an object has.
W = mg concerns weight. If W is your weight on Earth, then w = mg/6 is your weight on the Moon, since the gravity on the Moon is 1/6 that on Earth or g/6.
Is gravitational force an electrostatic force?
Question
March 11, 2009
Is gravitational force an electrostatic force? (i.e. it is NOT caused by matter)
John - Sweden
17430
Answer
Gravitational force is the attraction of objects of matter to each other. The objects usually don't have electrical charges.
Electrostatic force requires that objects be electrically charged.
Thus, two oppositely charged objects can attract each other by both electrostatic force and gravitational force.
Studying gravity and have some questions
Question
February 16, 2009
Hi , my name is Austin. I am working and studying gravity. I hope you don't mind a few questions. Well I was thinking if we can exhilarate the speed and force on gravity in one place it will crash what ever is in front of it is this true? . Well another question was that is gravity an atom or is just by itself in side a bigger atom? And the other thing was if gravity is inside a bigger atom will two atoms crash into each other cracking the two big atoms sending the two gravity atoms by them selves to push down any source of matter that it finds. Is it possible that this could be true or not well its okay if you can not answer this questions. If not thank you for taking your time to try. hear from you soon. Austin.
austin - USA
17286
Answer
Gravity is a force that attracts pieces of matter toward each other. Think of it like magnetism, except that there is no repulsion force (as far as we know). Even atoms have a gravity force that attracts other atoms toward them. But there may be other forces, such as electrical forces that prevent the atoms from smashing into each other.
Want to calculate force between two iron balls
Question
January 27, 2009
If you want to measure the gravitaional force between two objects at rest (say two iron balls sitting on the floor 1 foot apart), would you put the CENTER of the balls 1 foot apart, or would you measure the 1 foot distance between the outer face of each ball. In other words, do gravity measurements have to made using a distance equal to that from center to center?
thanks,
mack
mack - USA
17167
Answer
I assume you want to calculate the gravitational force, as opposed to measuring it.
The distance between two objects in the Universal Gravity Equation (see: http://www.school-for-champions.com/science/gravity_universal_equation.htm) is measured center to center. But this calculation is really an approximation that assumes the mass is concentrated at the center of each ball.
If the balls were small or very far apart, the approximation would be pretty good. But for two iron balls separated by only one foot, the calculation would not be that accurate. In such a case, you have to use some complex calculus to determine the gravitational force between the objects.
Even in the case of the two balls separated by one foot, using the Universal Gravity Equation would probably be sufficient to get an idea of the gravitational force between the two objects.
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Answers to Readers' Questions on Gravity