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Feedback Comments on Gravity

by Ron Kurtus

A total of 78 comments and questions have been sent in on Gravity. They are listed according to date.

You can read them to further your understanding of the subject.



List of next 10 letters

Topic

Title

Country

Gravity How can the velocity increase for falling objects? India
 
Gravity Would a person on the 100th floor weigh more? Canada
 
Gravity How does a rocket travel to escape the Earth's gravity? USA
 
Gravity Does not believe gravity is a force USA
 
Gravity Ideas and theories about gravity USA
 
Gravity Work done by freely falling object India
 
Gravity Acceleration due to gravity on the Sun Pakistan
 
Gravity Explanation of gravity of different sized objects Australia
 

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First 10 letters





How can the velocity increase for falling objects?

Topic: Gravity

Question

April 23, 2010

when objects falling on the ground has acceleration due to gravity of 9.8 m/s*s, then how can the velocity or speed increase of falling objects?

vijay - India

19590

Answer

Acceleration means the change or increase in velocity with respect to time. That means that every second the velocity is increasing.

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Would a person on the 100th floor weigh more?

Topic: Gravity

Question

March 23, 2010

Is gravity's pull increased at we move further away from the earth's core? If so is there an increase pull on say the 100th floor of a skyscraper then at street level?
Would a person living on the 100th floor perceive himself as heavier than a person of equal weight who lives at street level?
Thanks,
Ryan

Ryan - Canada

19422

Answer

Gravitation reduces as the distance from the center increases. The further you go from the center, the less is the force.

The force is gravity is fairly constant relatively close the Earth. For example, at 40 miles in altitude, the force is only 0.2% less than at ground level.

Thus a person on the 100th floor couldn't really tell the difference.

However, measurements on the top of a mountain show the force it greater due to more mass under the object.

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How does a rocket travel to escape the Earth's gravity?

Topic: Gravity

Question

March 1, 2010

Does a space bound vehicle have to circle the earth, on it's way to space, in order to acheive escape velocity or does it simply head straight out.

Larry - USA

19316

Answer

The escape velocity going straight up from the Earth's surface is about 26,000 miles per hour. That is so fast that the rocket will burn up from air resistance.

Typically, the vehicle is put in orbit where it then can be put into orbit at a considerably lower velocity. Also, the vehicle can use the rotation of the Earth to give it an added boost.

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Does not believe gravity is a force

Topic: Gravity

Question

February 21, 2010

Gravity is NOT a force.

Force DUE to gravity would be proper.

IF (And it is) F=ma then rewriting the equation replacing the general "a" acceleration with "g" for acceleration due to gravity we get;

F=mg

Again, IF Gravity was a force then mass would be a constant of dimensionless of 1 (Gravity = Gravity x m)

Gravity is NOT a force and never has been and never will be.

Kindly ask any physicist or engineer.

Thank you,

Dr. K. M. Schneider

Michael - USA

19261

Answer

The force is defined as a push or pull that accelerates or changes the direction of an object. Gravity or gravitation accelerates objects, and thus would be considered a force.

However, if gravitation is caused by a curvature of space-time, according to Einstein's General Theory of Relativity, it can be simply considered a property of space and not a force. A problem is that Quantum Mechanics still defines gravity or gravitation as a force.

The units for the acceleration due to gravity "g" are in meters per second squared. Multiplying that times the mass "m" in kilograms will give you the force and newtons.

See our lessons gravity and gravitation for a more thorough explanation.

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Ideas and theories about gravity

Topic: Gravity

Question

January 1, 2010

I have concluded that gravity really is an acceleration into time. The more mass an object has the more time has been warped there for the rate of acceleration increases in a linear portion,thus more G's are felt. One good example of this would be when an aircraft "Known as the Vomit Comet" goes into a cycle of rise and fall cycles, only as the craft begins to lose speed at top of cycle micro G's are apparent. After the aircraft begins to fall again and gains speed the micro G's are lost. My conclusion is that as the aircraft slows down that inertia of our bodies out accelerate the aircraft causing the effect of weightlessness. Just a thought that I have crunched on over the years to come to this conclusion. Also this would explain why objects of different masses fall at same rate here on earth or where ever a gravitational force is because there acceleration rates would be the same.

Ron - USA

18951

Answer

Einstein's General Theory of Relativity states that matter curves space, such that objects moving on a straight line follow the curve toward another mass of matter. His theory also states that time is a fourth dimension and calls it spacetime. So, to a degree your idea is somewhat correct.

Look at some of our other gravity lessons:
"Artificial Gravity" concerning G-forces:
http://www.school-for-champions.com/science/gravity_artificial.htm

"Effect of Mass on Acceleration Due to Gravity" at:
http://www.school-for-champions.com/science/gravity_acceleration_mass.htm

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Work done by freely falling object

Topic: Gravity

Question

November 21, 2009

hi, what is the work done BY A FREELY FALLING BODY. in my textbook it is written "work is done by the agent applying force". if it is correct then no work is done by the body.i had a huge debate over this with my friends. pls reply me. ur articles are gr8.
thanx for all ur help<

Gopal - India

18717

Answer

Work is the applied force times the distance traveled. In the case of a freely falling body, it is the work done by the force of gravity against the resistance of inertia.

For objects falling near the Earth, F = mg, where "m" is the mass of the object and "g" is the acceleration due to gravity (9.8 m/s/s). So, if the object or body fell a distance of "d", the work would be W = mgd.

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Acceleration due to gravity on the Sun

Topic: Gravity

Question

September 7, 2009

values of gravitational force on earth,sun and moon

shaheen - Pakistan

18264

Answer

You need to know the mass of the object to find the gravitational force.

The acceleration due to gravity on Earth is 9.8 m/s^2; on the Moon is 1.6 m/s^2 and on the Sun is 275 m/^s

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Explanation of gravity of different sized objects

Topic: Gravity

Question

February 7, 2005

I have no argument with you in your statement that the force of gravity on a body in space is largely dependent on the mass of that body (e.g. The Earth)
However you have made no mention of the capture area of the body in space have ing any relevence. Isuggest that if there were a sold ball of lead 100 ft in diamter floating in space, the gravity on that body would be considerably less that a ball of foam plastic with a diameter the size of the Earth. If gravity emminates from the 'Vacuum of space", then there must be a minimun diameter before gravity can be released from it's source.

Brian - Australia

5886

Answer

The force of gravity is proportional to the mass of the object and inversely proportional to the square of the distance. Thus the force drops off dramatically with distance. But that equation approximates the mass to be concentrated at the center of the object. The true equation taking into account the size of the object is more complex. But at great distances, the earth looks like a point.

A good explanation of gravity is from Einstein, where he says a mass curves space, just like placing a ball on a rubber sheet.

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