Gravity, force, and buoyancy

In summary, gravity and buoyancy are both forces. Gravity causes all mass in the universe to be attracted to all other mass, while buoyancy is caused by the pressure on the lower portion of an object being higher than the portion on the top, resulting in a force in the opposite direction of gravity. Buoyancy does not change the weight due to gravity, but it lessens the net force acting on a body. Buoyancy is not one of the four fundamental forces, but it is essentially gravity in action. When an object is submerged in a liquid, it is forced upward by the liquid's attempt to fall down, creating an upward force that can be seen by forcing the object down and raising the water level.
  • #1
Adam
65
1
Could someone please give me an accurate description of gravity, force, and buoyancy, and the relationships between them?

F=ma, or Fg=G*((m1*m2)/(d*d)) ? Which is used in which situation?

Does buoyancy affect weight, or merely counteract the effect of weight?

Stuff like that would be useful.

Thanks.
 
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  • #2
Both gravity and bouyancy are forces.

Gravity causes all mass in the universe to be attracted to all other mass.

Bouyancy is a force which is caused by the pressure on the lower portion of an object being higher than the portion on the top. The result is a force which points in the opposite direction of gravity.

It doesn't actually change the weight due to gravity, but it lessens the net force acting on a body.
 
  • #3
Buoyancy is NOT one of the four forces, correct?

Buoyancy itself does not reduce a thing's weight?
 
  • #4
F= GmM/r2 is the (Newtonian) formula for calculating the gravitational force between two objects of mass m and M at distance r apart.

F= ma is the formula for calculating the force (of any kind) necessary to accelerate an object of mass m at acceleration a.

"Bouyancy" is the upward force a liquid imparts on an object in the liquid: it's essentially the force the object has to exert (downward) to push the liquid out of the way. Whether it reduces the weight depends on exactly what you mean by weight. "Weight" normally is the force of gravity on an object- though sometimes, for convenience we take it as the NET downward force- if you do that, then bouyancy does reduce the net force by imparting an upward force.

No, bouyancy is NOT one of the four fundamental forces: gravitational, electro-magnetic, weak nuclear, and strong nuclear forces.
 
  • #5
Buoyancy is essentially gravity. A cork in water is forced up by the fact that the water is trying to fall down. The cork is trying to fall down too, but much more weakly than the water, so it loses out and let's the water fall down, thus forcing the cork up.

This is most easily seen by forcing the cork down in water in a smallish container. Forcing the cork under water visibly raises the water level. Thus work is reqired to push the cork down, because you are effectively lifting water by doing this.
 

1. What is gravity and how does it work?

Gravity is a natural phenomenon by which all objects with mass are brought towards each other. It is the force that holds the planets in their orbits and pulls objects towards the Earth's surface. According to Newton's law of universal gravitation, the force of gravity is directly proportional to the masses of the objects and inversely proportional to the square of the distance between them.

2. How does force affect motion?

Force is defined as any influence that causes an object to undergo a change in motion. It can accelerate, decelerate, or change the direction of an object's motion. According to Newton's first law of motion, an object will remain at rest or in uniform motion unless acted upon by an external force. The application of force can also cause an object to change its shape or size.

3. What is buoyancy and how does it work?

Buoyancy is the upward force exerted by a fluid (such as water) on an object that is partially or fully submerged in it. It is a result of the difference in pressure between the top and bottom of the object. According to Archimedes' principle, the buoyant force is equal to the weight of the fluid that the object displaces. If the buoyant force is greater than the weight of the object, it will float, and if it is less, it will sink.

4. How does the density of an object affect its buoyancy?

Density is a measure of an object's mass per unit volume. The density of an object determines whether it will float or sink in a fluid. If the object's density is less than the fluid, it will float, and if it is greater, it will sink. This is because the buoyant force is a result of the difference in density between the object and the fluid it is submerged in.

5. How does gravity affect buoyancy?

Gravity plays a crucial role in determining the buoyant force on an object. The force of gravity pulls objects towards the Earth's surface, while the buoyant force pushes them upwards. The net effect of these forces determines whether an object will float or sink. In lower gravity environments, such as space, objects may behave differently in terms of buoyancy compared to on Earth.

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