Upthrust and atmospheric pressure Flashcards
What does an object in fluid experience ?
Upthrust
When an object is submerged in a fluid what
happens to the pressure ?
The pressure of the fluid exerts a force on to the object from every direction.
Pressure increases with depth, what does this mean for the force acting on the
object ?
The force exerted on the bottom of the object is larger than the force acting on the top of the object. causing a resultant force upwards, know as upthrust.
What is the upthrust equal to ?
The upthrust is equally to
the weight of the fluid that has been displaced by the object. E.g. the upthrust on a pineapple in water is equally to the weight of a pineapple - shaped volume of water.
What happens when an objects upthrust is equal to the objects weight ?
Then the forces balance and the object floats.
What happens when an object weight in more than the
upthrust ?
The object sinks.
Whether or not an object floats depends on its ?
density
What happens when an objects upthrust that is less dense than the fluid it is placed in ?
The object weight less than the equivalent volume of the fluid. This means it displaces a volume of fluid that is equal to its weight before it is completely submerged.
What happens when an objects upthrust is denser than the fluid it is placed in ?
The object is unable to displace enough fluid to equal its weight. This means that its weight is always larger than the upthrust, so its sinks.
What does atmospheric pressure decease with ?
Height
Where is atmospheric pressure created ?
It is created on a surface by air molecules colliding with the surface.
As altitude increases, what happens to atmospheric pressure ?
It decreases.
This is because as the altitude increases, the atmosphere gets less dense, so there are fewer air molecules that are able to collide with the surface.
