Topic 5 Upthrust And Atmospheric Oressure Flashcards
What happens when an object is submerged in a fluid
The pressure of the fluid exerts a force in it from every direction
Why is the force exerted on the bottom of the object larger than the force exerted in the top
Pressure increases with depth
What is upthrust in liquid equal to
The weight of the fluid that has been displaced by the object
Why will an object float
If the upthrust of an object is equal to the objects weight then the forces balance
When will an object sink
If an objects weight is more than the upthrust
What does wether or not an object floats depend on
It’s density
Density causing an object to float
An object that is less dense than the fluid it is placed in, weighs less than the equivalent volume of the fluid this means that it replaces a volume of fluid that is equal to its weight before it’s completely submerged
therefore the weight is equal to upthrust so it floats
What happens to an object that is denser than the fluid it is placed in
Unable to displace enough fluids to equal its weight
This means it’s weight is always larger than it’s upthrust so it will sink
How do submarines rise and sink
Make use of upthrust
Large thanks are filled with water to increase weight of submarine so it is more than upthrust and will sink
To rise to the surface, the tanks are filled with compressed air to reduce the weight so it’s less than upthrust 
What is the atmosphere
Layer of air that surrounds the Earth and this thin compared to the size of earth
How is atmospheric pressure created on the surface
By air molecules colliding with the surface
What happens as altitude increases
Atmospheric pressure decreases
What happens as altitude increases
The atmosphere gets less dense so there are fewer air molecules that can collide with the surface
What does having fewer air molecules above the surface is height increases mean
The weight of the year above it which contributes to atmospheric pressure decreases with altitude
