myfriend tells me that inertia keeps the earth going around the sun. How is this true and not true?

Question

Detaild response please

Answer 1

Your friend is half right. What keeps the earth in orbit is the gravitational pull of the sun. Why doesn't the earth crash into the sun? Because the inertia of the earth (or any other object in an orbit) is always at a right angle to the centripital force.

Centripital force is literally the center seeking force. It is always directed to the of the orbit. The velocity or direction of motion is always at a 90degree angle to this force. Since the direction of motion and acceleration are always changing, the object can be constantly accelerating and constantly in motion without ever getting any closer to the center.

Answer 2

Inertia is the property of matter to continue moving, at a constant speed in a straight path, while in motion, or to stay stationary when at stop, when there is no unbalanced outside net force acting on the object. The inertia of the earth keeps it moving around the sun. But take the point: "... in a STRAIGHT path..." so, it is now the centripetal force. Take note that it is regarded that centrifugal force is an UNREAL force, and of which does NOT exist. The centripetal force exerted by the sun on the earth, contradicting the earth's inertia, forces the earth to form its orbit.
I am not that sure about that,
but i hope it helps...

Answer 3

Actually I believe that it is a combination of inertia and gravity that keeps the earth going around the sun. Inertia is basicly the movement of the earth in its orbital path around the sun. But without the sun's gravity pulling on the earth, the earth would simply be floating through space and we would all be frozen due to lack of heat that our sun provides.

Answer 4

I have read all answers. In my opinion the concept of inertia should be completely banned from any discussion. It creates more confusion than clarification. If you ask persons who advocate this concept, what is its measure, they would perhaps say mass. If it is so why to talk about inertia at all. Let us all the time talk about mass and not inertia. If we think of mass we do not think that it can do anything. But if we think of inertia then we think inertia does something at least it stops something from happening. By definition, inertia does nothing so naturally it has no business to turn the earth around the sun. Please detach yourself from the earth and from some point deep in space will you not find that earth is neither at rest nor moving in a STRAIGHT LINE, then some external force must act on it that is what Newton's first and second law tell us. This is how the question is misplaced hence not true.

Now how it can be true. Strictly speaking, Newton's laws hold good only in inertial frame that is why I asked you to go out of the earth as you wanted to comment on its motion. It is obvious that Newton's law does not hold in accelerated frame. Suppose you are attached to an object having acceleration in some inertial frame. Then there must be some known external cause/interaction for this, one can very easily see that. Now consider the motion of the object in its own frame or your frame as you are attached with it. You have to say that object is at rest in your frame which is attached with it. So if you apply Newton's law then you would say that no net force should act on it. But you are already aware that some external force is acting and producing acceleration 'a' given by F = ma. Now if you want that Newton's laws should be valid for this accelerated frame also then you may say that a force equal to ma is acting on the body in opposite direction. Such a force is unfortunately given the name "inertial force" although it is considered only in non-inertial frames and is not because of any known fundamental interaction. So one may say that in its own frame earth is at rest being pulled by sun in one direction and pushed by some force equal to ma in a direction opposite to sun.
This force is also called centrifugal force or pseudo force but on that some other time.

Answer 5

Inertia keeps the Earth moving around the sun. That true. It's not-not true.

What exactly are you asking?

Answer 6

Inertia keeps the Earth rotating on its axis and moving in space.
Gravity keeps the Earth revolving around the sun.

Answer 7

Inertia is the capacity of objects to keep doing whatever it is they are doing. If that are at rest, they remain at rest. If they are moving, they keep on moving. The only way to change the speed of an object is to apply a force on it.
Apart from the gentle gravitational tug of other planets, and the tidal effect of the sun and moon, plus the sun's radiation pressure, the Earth is not subjected to external forces that can significantly alter its orbital characteristics, so it keeps going round and round the sun, because of its inertia.
So, it turns out your friend is right.

Answer 8

Inertia is only part of the story. There is a strong centripidal force that propels the earth outward away from the sun. The sun's strong gravity pulls the earth toward it. The two forces counteract each other, keeping the earth in orbit around the sun.

Answer 9

ya. inertia makes us go around the sun. it true.

Answer 10

It is so.