# 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

### Country

Overview of Gravity Escaping gravity USA

Center of Gravity Find the CG of combined figure Kenya

Effect of Gravity on Sideways Motion Which hits the ground with the greatest speed? Canada

Effect of Gravity on Sideways Motion Wants permission to use image in his book USA

General What is the meaning of an equation South Africa

Gravity Constant Factors Effect of Earth's rotation on flying India

Work Against Gravity Force opposing gravity India

Velocity Equations for Objects Projected Upward Potential energy with a floating balloon Pakistan

Mass and Weight Changing weight reading on a spring scale India

General What effect does gravity have on structures? South Africa

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First 10 letters

## Escaping gravity

Topic: Overview of Gravity

### Question

March 21, 2014

QUESTIONS:

1. Is there any law or theory that oppose the force of gravity?
2. What object goes up and never come back as in resisting the force of gravity.

Iferi - USA

24803

### Answer

There are some theories about anti-gravity, which is the opposite of gravity. But they have not been proven.

An object that goes up and does not come down must move at a velocity greater than the escape velocity of gravity. See Escape Velocity from Gravity.

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## Find the CG of combined figure

Topic: Center of Gravity

### Question

February 24, 2014

how can you find cg of a combined figure with triangle rectangle and a semicircle

collins - Kenya

24554

### Answer

Although there are geometric methods to find the center of gravity of various shapes, they can be quite complex.

The most common method to find the CG of an item is hang it from several points on its surface along with a plumb line or weighted string. The intersection of the plumb lines would be the CG.

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## Which hits the ground with the greatest speed?

Topic: Effect of Gravity on Sideways Motion

### Question

January 28, 2014

so, which hits the ground with the greatest speed; the bullet or the casing?. thank you

tomi - Canada

24469

### Answer

The casing usually is ejected slightly upward, so it is falling from a greater height and will hit the ground at a slightly greater vertical speed than the bullet. Also, it would reach the ground after the bullet hit the ground.

However, if you simply dropped a casing at the exact time the bullet left the barrel, both would hit the ground at the same time an at the same speed.

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## Wants permission to use image in his book

Topic: Effect of Gravity on Sideways Motion

### Question

December 27, 2013

Hello. I am writing to ask if I may have permission to use an image on your Web page www.school-for-champions.com/science/gravity_sideways_motion.htm for a book I am writing, which will be published by NSTA. The image is the one of the balls dropped and thrown sideways. Thank you very much. --Matt

Faculty, University of Maryland

Matthew - USA

24387

### Answer

Yes, you have permission to use the image in your book, provided you cite the source.

Best wishes in completing your book. Let me know when it is released.

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## What is the meaning of an equation

Topic: General

### Question

November 23, 2013

what is equation meaning?

unaib - South Africa

24218

### Answer

In Algebra, an equation is a statement where the operations on the right side of the equal sign equals those on the left side.

In Physical Science and Physics, the letters or unknowns represent physical measurements. Thus, the equation F = m*a represents the force equals the mass times the acceleration.

Often science equations are called formulas.

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## Effect of Earth's rotation on flying

Topic: Gravity Constant Factors

### Question

October 4, 2013

Q. in every 12 hrs the earths rounds half and india bacome america bt we need 22 hrs to travel to america in aeroplane why ???

Rohit - India

24076

### Answer

The time it takes to fly from India to America is 22 hours, because the speed of an aeroplane is with respect to the air or atmosphere and not the ground. When the Earth rotates, it drags the atmosphere with it at approximately the same speed. Otherwise, you would feel a wind of 1667 kph on the ground.

However, if you were in a space satellite that was moving above the atmosphere, the rotation of the Earth would make a difference in which direction the satellite traveled.

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## Force opposing gravity

Topic: Work Against Gravity

### Question

September 25, 2013

1. what are the force that can oppose the gravitational force?
2. Is it possible to withstand against the gravitational force?
3. can the object moves with high velocity against the gravitational force?

velvizhi - India

24052

### Answer

On Earth, any upward force greater than the weight of the object will overcome gravity.

Objects moving upward at high velocities can even escape from the gravitational force of the Earth. See Escape Velocity from Gravity for more information.

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## Potential energy with a floating balloon

Topic: Velocity Equations for Objects Projected Upward

### Question

August 30, 2013

How the ballon have potential energy when it going upward?

fida - Pakistan

23980

### Answer

If a balloon is filled with helium, it will float upward. But also, the higher an object is off the ground, the greater its potential energy with respect to gravity.

If the balloon loses its helium gas, then gravity will take over and it will fall to the ground.

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## Changing weight reading on a spring scale

Topic: Mass and Weight

### Question

April 12, 2013

Hello sir,
I wants to know that can a change in the value of 'gravitational acceleration' change the reading of spring scale?
Thanks

Utkarsh - India

23613

### Answer

The reading on a spring scale is due to the weight of the object: W = m*g, where "W" is the weight, "m" is the mass and "g" is the acceleration due to gravity.

The value of "g" can change at high altitudes or on an object like the Moon. That means that the weight or reading on a spring scale would be different.

See Mass, Weight and Gravity for more information.

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## What effect does gravity have on structures?

Topic: General

### Question

April 11, 2013

What effect does gravity have on structures?

Reshoketsoe - South Africa

23609

### Answer

Gravity cause the weight of a material. A structure must be able to withstand its own weight.

For example, a concrete bridge must be able to withstand the weight of its concrete. It the span is too long for its strength, gravity was cause the bridge to collapse.

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## Summary

Hopefully, this reader feedback has helped provide information about Gravity issues.

Appreciate what you have

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### Websites

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