# Gravity

## One of the four fundamental interactions, gravity is responsible for the fact that any objects with mass attract one another. According to general relativity, it is a space time curvature, but according to quantum mechanics it is the result of exchanges of virtual gravitons.

### What is mass divided by weight? ### Does doubling the distance between two objects half the gravitational force between them? No, that reduces it to one quarter, not to half. In the equation for gravitational force (F=G(m1m2/r2) the distance is squared, so doubling the r (2r2) results in the two in front of the r also being squared, resulting in 1/4 the force. This is the same for electrical force which is a similar equation ( F=K(q1q2/r2). Likewise, halving the distance quadruples the force, it does not double the force.

### What is gravity override? This is a problem encountered with extraction of Petroleum from the ground. Petroleum engineers use steam flooding processes to extract the oil from a reservoir. The Phase relationships of steam, water and hydrocarbons are critical to this process and can result in either Steam override or Gravity override. A physical characteristic of steam injection processes that must be considered is steam override due to gravitational forces. Gravity override is caused by the fact that steam is much less dense than liquids and therefore will tend to rise in the porous medium. At the same time, hot water produced by the condensation of steam is more dense than some contaminants, so may tend to underride the zone to be treated. When there is a difference in density between the injected fluid and the fluid initially present, the slope of the interface between the fluids is equal to the difference between the vapor and liquid water phase viscous forces divided by the gravitational forces. The degree of gravity override increases as the difference in density between the liquid and vapor phases increases, as the permeability of the medium decreases, and as the viscosity of the liquid phase being displaced increases. One operational parameter that affects override is the steam injection rate. Source: Steam Injection for Soil and Aquifer Remediation by Eva L. Davis

### Why can't we feel our own gravitational pull? We feel our gravitational pull on the Earth every day. The Earth is the only object large enough and near enough that it can exert a force which we would notice.

### Find the change in the force of gravity between two planets when the distance between them is increased by a factor of five? The force of gravity varies as the inverse square of the distance, so if the distance were increased by a factor of five, the force between them would decrease by a factor of five squared, or 25. So the new force would be 4% of the original force.

### What is Saturn's surface gravity? 0.92 (times Earth's surface gravity). Edit : OK this one is a bit tricky. It is usually given for Saturn's equator. It does depend on latitude. Also the rotation speed affects the "apparent gravity" because of "centrifugal force", but this doesn't affect the underlying force of course. So you will see some variation in the figures quoted, depending on definition, etc. I looked at a NASA pages for this and they give two different values. One is the answer above, given by a previous contributor. The other value is: 1.065 x Earth's. Most sources seem to agree things would weigh a bit more on Saturn, but it's a bit confused.

### Can a magnetic force be stronger than gravity? Of the four fundamental interactions, gravity is the weakest force by far. electromagnetic forces are almost always stronger than gravity. The other two forces are weak nuclear force and strong nuclear force. <><><> Consider the electromagnet crane used to move metal in scrap yards. The magnetic force is lifting material against the pull of gravity- it must be stronger in that spot. If the magnet is strong enough to keep a object attached while lifted, and the object does not drop, the force between that object and the magnet is stronger than gravity, otherwise...it would drop. Just as the upward force of our legs is obviously greater than the downward force of gravity, or we couldnt stand

### Why does the moon have less gravity? The moon has less gravity, because its mass is smaller. Gravity of an object like the moon or a planet is related to its mass. The more mass, the higher the gravity. The equation for force due to gravity is F=G(m1m2/r2 , therefore decreasing on mass (in this case the moon has less mass than the Earth) lessens the force of gravity. So the above answer was correct this just is a explanation using the equation which hopefully helps the understanding. By the way, if 2 humans were left in a vacuum, quite close to each other, they would slowly move closer to one another. This is because humans have mass therefore they have a gravitational field.

### Does gravity have a color? Gravity is the force that causes objects to attract each other. Gravity is not an object, therefore it has no color.

### Why are the free falling bodies weightless? A free falling body appears to be weightless because gravity is the only force acting on it. There is no ground or floor to stop the fall so the body "floats" in the air as if weightless. A space ship in orbit is falling around the earth, and everything inside it is falling at the same speed, so to the astronauts inside the ship it feels as if there is no gravity. However, really gravity exists no matter where in space, so it is not TECHNICALLY possible to be weightless, which is why the term free falling is used.

### How is helium affected by gravity? Gravity works on Helium the same as it works on everything else. But the higher air pressure at sea level (caused by gravity compressing air particles at the surface) works against Helium to squeeze it upwards. This effect is called buoyancy, where a fluid of lesser density (Helium) is pushed away by a fluid of higher density (normal air). It's the same effect you see when a ball full of air is pushed into water.

### Why does lubricant decrease friction? The basic idea of friction is to fitting the ups and downs of one surface into the ups and downs of other surface. Mostly, we cannot see ups and downs of surfaces with our naked eye as it is in molecular level. This lubricant's molecules goes and fits in to the ups and downs of our required surface and makes surface smoother so that these ups and downs of other surface cannot fit into the required surface. Thus lubricant reduces the friction.

### What does surface gravity measure? "Surface gravity" is simply the strength of the gravitational field of a planet (or other object) at its surface. Often it is measured as the "acceleration due to gravity". On Earth this is about 9.8 meters per second per second.

### When is an object truly weightless? When there is no gravity. Weight is the affect of gravity on a object. Objects in orbit or objects that are falling still have weight. In fact, and object in orbit around the Earth is in essence falling the entire time, but it never hits the ground because while it falls, the Earth is curving away beneath it. There is no spot in space with no gravity, but there are spots where the gravitational forces cancel each other out. This is where an object can be weightless. (For example, if you were between the moon and the Earth, and both were pulling on you with the same gravitational force.)

### What kind of energy is a pogo stick on impact? It is kinetic energy, pertaining to motion. It is compressed energy, the spring in the stick is in Compression, this energy will be released when the weight on the stick is removed.

### Is the moons gravity one sixth of earth? As good as. If you weigh 100 lbs on earth, you would weigh 16.54 lbs on the moon. One sixth of 100 equals 16.6666.... Close enough.

### How does the force of gravity between two bodies change when the distance between them is increased by 4? Provided neither mass changes, the mutual gravitational force of attraction between two bodies decreases to 1/16 of its original value when the distance between their centers increases to 4 times the original distance.

### Who first discovered neutron? An English physicist named James Chadwick discovered the neutron- winning him a Nobel Prize in Physics in 1932.

### What happens to flame in zero gravity? When something burns, like a candle for instance, the substance acting as the fuel (e.g. the wax) becomes very hot and vapourises. Because the vapour is hot, and expands, it has a lower density than the surrounding air so it rises upwards. As it rises it mixes with oxygen in the air and the mixture burns. The hot gases produced continue to rise out of the way, and the extra heat produced vapourises more fuel so that the process can continue. But in space, where there is no gravity, there is also no density gradient so the hot gases can't rise. Instead they accumulate in place and starve the flame of a supply of fresh air, so it goes out. The only way to maintain a flame is to artificially blow in oxygen to ensure that there is sufficient to support combustion.

### Why does mass have gravity? That's a really good question that a lot of physicists would like to know the answer to. One theory is that it has to do with a particle called the Higgs boson which has been predicted but never observed. One of the things scientists at the Large Hadron Collider will be doing is looking for the Higgs boson.

### How does the suns gravity affect the solar system? Answer 1 It keeps the planets in orbit. Without something to pull us in, because also each planet has it's own attraction and repel force so that's also the second reason why the planets are stable in there own orbit and they not go far away. __________________________________ Answer 2 Our sun plays a very small but important part in helping to keep all other bodies in our Solar System in their proper orbits. I say small because our solar system is also affected by other systems beyond our own. Certainly our system would still be there if the sun were to disappear, but you would find that because of its lack of gravitational effect on our system our position in the solar system would change. ____________________________________ Answer 3 It keeps the planets in orbit. Our sun plays a vital part in helping to keep all other bodies in our Solar System in their proper orbits. The system would not be there if the sun were to disappear because the lack of gravitation would cause everything to fly off at a tangent.