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<div id='flashcontent'>Blogumulus by <a href='http://www.roytanck.com/'>Roy Tanck</a> and <a href='http://www.bloggerbuster.com'>Amanda Fazani</a></div>
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The question pose is as follows : The horse pulls the cart by a force F₁ in the forward direction. From the third law of motion the cart pulls the horse by an equal force F₁=F₂ in the backward direction . The sum of these forces is , therefore , zero . Why should then the cart accelerate forward ?

Try to locate the mistake in the argument. According to our scheme, we could first decide the system. We can take the horse as the system or the cart as the system. Suppose you take the cart as the system .Then the force on the cart is F₁ in the forward direction .How much is this acceleration ? Take the mass of the cart to be Mr.’s the acceleration of the cart a = F₁/M_C in the forward direction ? Think carefully . We shall return to this question.

Let us now try to understand the motion the horse. This time we consider the forces on the horse. The forward force F₁ by the gorse acts on the cart and it should not be taken into account when we discuss the motion of the horse. The force on the horse by the cart is F₂ in the backward direction. Why does the horse go in the forward direction when whipped ? The horse exerts a force on the cart in the forward direction and hence the cart is accelerated forward . But the cart exerts the equal force on the horse in the backward direction ? Where are we wrong ? We have not considered all forces acting on the horse. The road pushes the horse by a force P which has a forward component. This force acts on the horse and we must add this force when we discuss the motion of the horse. The horse accelerates forward if the forward component f of the force P exceeds F₂ acceleration of the horse is (f-F₂)/Howe should make sure that all the forces acting on the system are added .note that the force of gravity acting on the horse has no forward component.

Going back to the previous paragraph the acceleration of the cart may not be F₁/M_C.The road exerts a force Q on the cart which may have a backward component f’ .The total force on the cart is then a = (F₁-f’)/M_C in the forward direction .

The forces f and f’ are self adjustable and they so adjust their values that (F₁-f’)/M_C = (f-F₂)/M_H . The acceleration of the horse and that of the cart are equal in magnitude and direction and hence they move together .

So, once again we remind you that only the forces on the system are to be considered to discuss the motion of the system and all the forces acting on the system are to be considered Only then apply F=ma

The sun will pull the moon out from a perfectly spherical orbit. In this make-believe problem, does the moon orbit around the planet's equator? And does the planet orbit the sun around the Sun's equator? Also, is the planet's spin axis perpendicular to it's solar orbit, or is it tilted?

Unless everything is perfectly aligned, the orbits will be "chaotic". This does NOT mean that it goes wild all over the place. It just means that the orbit will be elliptical, and the amount of ellipticalness will very over some (small) range, in an unpredictable way (slow changes over time). Also the orbits' obliquity will change chaotically.

To prove this would take more than just Newtonian physics. You would need some general relativity also.

To get a simulation of the chhange in moon's orbit just click here
Wanna understand about the changes of the moon's phases ? click here

This picture gives a clear idea of how the orbit changes its angle.

Why This happens ?

The earth is in place with other planets because of the huge gravitational force exerted by the sun on the earth .

The magnetic poles of sun and Earth are not static and they keep changing after a long period of time , so the when the gravitational/magnetic poles of the sun changes even the orbit of the earth changes because the earth orbit depends on the sun and other planets

Fireworks

Fireworks have been around for hundreds of years. They consist of either black powder (also known as gunpowder) or flash powder in a tight paper tube with a fuse to light the powder. Black powder, contains charcoal, sulfur and potassium nitrate. A composition used in a firecracker might have aluminum instead of or in addition to charcoal in order to brighten the explosion.




Sparklers

Sparklers are very different from firecrackers. A sparkler burns over a long period of time (up to a minute) and produces extremely bright and showery light. Sparklers are often referred to as "snowball sparklers" because of the ball of sparks that surrounds the burning portion of the sparkler.You can see that a sparkler consists of several different compounds:

• A fuel
• An oxidizer
• Iron or steel powder
• A binder

The fuel is charcoal and sulfur, as in black powder. The binder can be sugar or starch. Mixed with water, these chemicals form a slurry that can be coated on a wire (by dipping) or poured into a tube. Once it dries, you have a sparkler. When you light it, the sparkler burns from one end to the other

Why sparklers do not burst ?

The fuel and oxidizer are proportioned, along with the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker.

What is Diamagnetism ?

Diamagnetism is the property of an object which causes it to create a magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. It is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field.

Diamagnetic Levitation

Many common materials such as water, wood, plants, animals, diamonds, fingers, etc. are usually considered to be non-magnetic but in fact, they are very weakly diamagnetic. Diamagnets repel, and are repelled by a strong magnetic field. The electrons in a diamagnetic material rearrange their orbits slightly creating small persistent currents which oppose the external magnetic field. Two of the strongest diamagnetic materials are graphite and bismuth.

The forces created by diamagnetism are extremely weak, millions of times smaller than the forces between magnets and such common ferromagnetic materials as iron. However, in certain carefully arranged situations, the influence of diamagnetic materials can produce startling effects such as levitation.

It was proved in 1842 that it is impossible to stably levitate any static array of magnets by any arrangement of fixed magnets and gravity. However, the addition of diamagnetic materials makes such levitation possible. The July 22 Nature paper,Magnetic Levitation at your fingertips,describes two configurations where diamagnetic materials are used to stabilize the levitation of a magnet in the field of a fixed lifting magnet.

Revolution

The Sun does revolve around the Milky Way on an almost circular orbit with a speed of about 220km/s. The Sun completes one revolution in about 230 million years. The Milky Way also moves - we are moving towards or nearest neighbour the Andromeda galaxy and both the Milky Way and Andromeda (which make up most of what we call the 'Local Group of galaxies') are moving towards the Virgo Cluster which is our nearest cluster of galaxies. Nothing seems to stand still at all

Rotation

The sun certainly does rotate ,it has a rotational period of about 25 days. This is apparent if you have ever used a telescope to project images of the sun onto a piece of white card so that you can see the sunspots. If you do this over several days, the sunspots appear to move across the face of the sun. Not only does the sun rotate, but it also orbits the centre of our galaxy, completing one orbit every 226 million years or so.

What I Think !

Hey i think the scientists had a tough job to find whether the run is rotating.I have a simple idea

Why not we just observe some spots on the sun and then make a note of it and see if the spots/identifications appear again. Simple ! But I'm sure the scientists must have found some flaw in this method !