Every thing exists under the same laws of Gravity. many things seem lighter in a swimming pool because they are relatively lighter in a heavy medium like water rather the light medium like air. Nearly every thing falls to the ground in air. however there are a lot of things that float or go up in water because they are lighter then water. this rule applies to every thing even things that sink.

Well you see... it really helps to have a driver as good as Jeff Gordon behind the wheel of a racing machine. Jeff Gordon is god

the center of the universe depends on your vision and point, its all a form of opinion. Everyone can consider themselves as the center.

You can expect the specific gravity to be close to that of water, since it will consist mainly of water. The exact specific gravity will depend on the type and amount of impurities still present - which in turn will depend on what the sewage was like BEFORE being treated, and on the treatment process used.

A bicycle

A truck

. A camel

Tennis balls are affected by the environment in a few ways. The environment can affect how it bounces. Warm air makes the ball expand causing it to have a higher bounce. Cold air makes the ball contract and can make it harder to bounce.

Gravity is one of the most important factors to know for gymnastics. It is important that gymnasts have to work with the force of gravity because of all the flips and turns they have to do.

This is because it slows you down and it means that you will get hot feet

The human body is constructed to exist in a gravitational environment; everything from blood flow to our sense of balance is influenced by the gravitational pull of the earth. Astronauts who spend protracted periods of time in weightless conditions suffer a number of physiological problems, from chemical imbalances and decalcification of bones to heart irregularities.

They have fuzz on them so the air the ball is traveling through can grip the ball to enhance the spin on the ball. ex. To move it farther (backspin) or to make it drop (topspin) or to make it curve to the side (sidespin). The fuzz also allows the ball to have better interaction with the surface, the air and the racquet. As the ball speed increases the fuzz filaments lay down on the ball and the fuzz drag declines.

The tennis ball cover is rough but not like sandpaper. Looking closely at the felt you can see that air flows through those raised fabric filaments - better known as fuzz. So the surface of a tennis ball is a "porous surface." It's more like dealing with the wind blowing through leaves on a tree and just as complicated. The fuzz filaments act like tiny cylinders each having their own drag component. In addition to the skin friction drag from the cover itself, drag is created from the airflow over these fuzz fibers interacting with all the other fibers behind it.

Every tennis racquet is marked by the manufacturer with the recommended range of tensions. For example most medium sized racquets can be strung from 22Kg up to 28Kg. For maximum control the higher tensions are best. For maximum power the lower tensions are best. For a good mixture of both control and power the tension should be midway - that is 25Kg in the above example. The thickness or gauge of the string will also effect the power. A racquet tension of 25Kgs with a thin (1.20) string will produce more power than a tension of 25Kgs with a thick (1.35) string. If your average shot is falling nearer the service line than the baseline then either lower the tension 1 or 2 Kgs or use a slightly thinner string to get more shot distance. However, be warned, a thinner string is not as durable as a thicker string so it may need replacing more often. If your average shot is going off the end of the court then either increase the tension on your racquet by 1 or 2 Kgs or use a thicker string (or both) to reduce the shot distance. Developing more topspin on your shots will also bring the ball down earlier - so there are many more factors than just racquet tension and string size to consider. An oversize racquet (i.e. the head is larger) will also produce more power since the central sweet spot is larger and also the strings produce more of a trampoline effect. A heavier racquet will also produce more power but you may lose a degree of control due to the difficulty of manoeuvring the extra weight. As a generalisation a keen amateur would probably play best with a medium size racquet, a string tension of around 25Kgs, a string size of around 1.25mm, a racquet weight of around 300gm and a desire to hit topspin whenever possible. However the question "What tennis racquet tension makes you hit a ball harder?" may not be as important as "Which tennis racquet set-up will help me hit more accurately?" The last thing to mention is that the size of the grip on a tennis racquet (between 4" to 5") is crucial to hitting accurately and powerfully. Always buy a racquet with a grip that your hand can go nearly all the way round (4 1/8" or 4 1/2" for most adults). A grip that is too big will produce poor tennis and cannot be reduced. Whereas a grip that is comfortable will produce better tennis and the grip size can always be increased later if necessary.

Without friction they would slide around the pitch like a bunch of air-hockey pucks. Friction allows them to run and make cuts. It also means that the ball will slow down after being kicked so they can stay with it if they want to and continue to make small kicks to control it's direction. Friction allows the goalie to push off from the ground to launch himself/herself into the path of the ball to block goals.

"rain"

No. The gravity that comes from the Sun pulls us towards the Sun. The gravity that comes from Earth pulls us towards Earth.

No one knows for certain what gravity is.

Newton explained how gravity acts but not what gravity is.

Einstein's General Theory of Relativity says that gravity is the warping of spacetime in response to the presence of mass and objects then following the warped paths resulting in spacetime. This model has explained many previously known observations (e.g. the anomalies in Mercury's orbit) that Newton's work could not and made predictions (e.g. bending of light paths by gravity, black holes) nobody could have otherwise imagined.

However even the explanation of General Relativity about gravity may not be complete or totally correct. If Quantum Mechanics and General Relativity can someday be successfully combined it may again be necessary to change our understanding of gravity.

Yes, weight is the force of gravity on an object. Which is why you would weigh less on the Moon. An object on the Moon will weigh only 16.6% of what they weigh on the Earth.