If gravity between the Earth & Moon is a pull (attraction)Then why is there a centrifugal force(repulsion)?

Answer 1

There are some very technical, and very correct explanations here. I will try to explain it without using quite as much physics jargon so that it might be easier to understand.

There is no "centrifugal force." We've all ridden amusement park rides that go in circles, and felt ourselves "thrown to the outside" of the seat, so this seems like an untrue statement. However, if you stop and think a moment, you'll see why it is true that there's no centrifugal force, but the motion feels this way.

Think of a simpler example. You are in a sports car, and you stomp the gas. You're "thrown back in the seat." You aren't really being thrown back; nothing is pushing you backwards at all. What's happening is the car is accelerating very quickly, and you're feeling the seat of the car pushing up behind you, and bringing you along to the same speed as the car. (If you didn't speed up with the car, the seat would rip out the back of the car as the car sped out from around you - like in a cartoon)

Whenever you get to the speed you want to go, you ease off of the accelerator, and you're no longer being "thrown back in the seat." You're now moving at the same speed as the car, and neither you nor the car is changing speeds, so you feel the same forces as if the car were sitting still. (except for the road vibrations, of course)

When you slam on the brake, you're "thrown forward" into the seatbelt (hopefully). You're not really being thrown forward at all - the car is slowing down, and then the seatbelt is pulling you back to slow you down with it. Otherwise, you'd end up as a chalk line on the street in front of the car!

Now that you can see a simple case of where common language is actually misleading, apply that to circular movement.

In order to change motion, it requires acceleration. The car accelerates to speed up or to slow down. (braking is actually just negative acceleration). If there's no acceleration, there's no change in the motion of the car - it just keeps moving at the same speed, and in the SAME DIRECTION. Changing direction is acceleration, too.

This is what makes motion bend into circular paths: the moving object is constantly being accelerated towards the center of the circle. As soon as the center-seeking (centripetal) acceleration stops, the motion returns to a straight line. Instantly! Imagine the spinning yo-yo example, when the string breaks. If the direction you're facing is 12 o'clock, and the yo-yo is spinning clockwise, if the string breaks at 12 o'clock, the yo-yo will fly off in the 3 o'clock direction. If you wanted it to fly off in front of you, you'd have to let go (or the string should break) when the yo-yo is at 9 o'clock.

So each instant you are moving in a circle, you're being accelerated at the center. Remember what acceleration feels like in the car? It feels like being "thrown back" in the seat, but in truth, the seat is pushing you forward. This is what's happening in the circular motion: You're being "thrown back" in a "seat" that is facing the center of the circle, and each moment you move along the circle, the chair is turning to always stay facing the center. This is why you feel like you're being thrown to the outside of a circle, just like being thrown back in a car seat.

For orbiting bodies in space, gravity is the force which supplies the acceleration that keeps them moving in circles, just like the yo-yo string supplies the force that accelerates the yo-yo into a circle.

As far as the "balance" between centripetal acceleration and "centrifugal force" is concerned, the actual balance is between gravity and the momentum of the orbiting body. If Earth's gravity were stronger, then the moon, moving at the same linear speed, would be orbiting further from the Earth to maintain a stable orbit. If the moon were orbiting at the same distance but with higher gravity, then it would be moving faster than it is now.

Answer 2

Centrifugal force is an illusionary force caused by the frame of reference changing speed/direction. What you need to think about is centripetal acelleration, which acts as you would expect in the same direction as gravitational attraction.

So, what is this illusion, and how can it be explained? It occurs in all circular (and elliptical or cornering) motion so lets use a simpler example, the physics is the same:

You are ina car, it takes a right turn and your feel yourself "pushed" into the left hand side of the car. You are not pushed at all, the car moves to the right, your momentum keeps you going straight, you are therefore no longer going in the same direction as the car so you are accelerated to the right by the car.

Remember that when doing Newtonian Mechanics you must ALWAYS use an inertial frame of reference, the reference point you use must not accelerate (ie change speed or directions) or illusionary forces appear.

Another good example is a train slamming on its brakes, you see a bag "accelerate" up the corridor ! Again, an illusion due to the frame of reference (the train) not being inertial.

Answer 3

that's by using fact there is an equilibrium between the Earth's gravity and the Moon's inertia. The inertia (which many human beings mistakenly call centrifugal rigidity) is the tendency of a moving merchandise to maintain on moving in a at present line. The Moon consistently strikes previous the Earth. The Earth tries to tug it in direction of itself. The Moon tries to maintain on going interior the direction it replaced into going. the end result between those 2 forces is the orbit of the Moon around the Earth. In different words, the Moon IS falling, inspite of the shown fact that it keeps going previous the Earth and actually misses it, having to maintain going around and around.

Answer 4

Centrifugal force is not actually a real force in physics. There is only centripetal force, the force pulling the object toward the central point, and the tangial inertia of the object.

In otherwords, when you take a yoyo on a string and spin it around, the circular motion of the yoyo is a product of only two vectors: the tension the string exerts on the yoyo to hold it in, and the inertia of the yoyo in a straight line.

all of this is proven by looking at the path the yoyo takes if the string is cut.

Answer 5

The moon moves around Earth at 2,286 mph. That speed is constantly trying to throw the moon away from Earth. At the same time Earth's gravity is trying to pull it down. The two factors cancel each other and the moon moves around Earth.

Answer 6

The moon stays in its orbit because the centripetal force (gravitational attraction) is just balanced by the centrifugal (outward) force. If they were not in balance, the moon would either fall down or drift away.

Answer 7

ill give you the easy answer. think about it like this....gravity wants to pull things together right, well if you had a ball on a string and you started spinning around in a circle while holding on to the string and then let go of the string, the ball would want to fly away, right????? this is the same principle you are talking about. i hope this helped!!!!!!!

Answer 8

In the words of the Geico Caveman (ahhhh What?)