Physics Pressure, Buoyancy

Vector/scalar

physical quantity with a magnitude and a direction / physical quantity with a magnitude

state of matter solid

Particles have fixed positions and are close together. The attractive forces are very strong.

Vector/scalar

physical quantity with a magnitude and a direction / physical quantity with a magnitude

state of matter solid

Particles have fixed positions and are close together. The attractive forces are very strong.

state of matter liquid

Particles don‘t have fixed positions and are farther apart. The attractive forces are strong but weaker than in the solid state.

state of matter gaseous

Particles move around freely and are very far apart. The attractive forces are weak.

Why do most objects expand when they warm up?

The particles get more energy and start moving more, thus they need more space and the object expands.

Are gases compressible?

They are, there is a lot of space between the particles and the attractive forces are very weak.

Are liquids compressible?

They are not, as there isn‘t enough space between the particels and the attractive forces are too strong.

pressure

a force distributed over an area exerts a pressure

Pascal‘s principle

A change in pressure at any point in a motionless fluid or gas enclosed in a container is transmitted to all points in the fluid.

What is the cause of pressure in a liquid (fluid pressure)?

The weight of the column of water above.

What is a good rule of thumb for water pressure?

Water pressure increases every ten meters by one bar.

What is a good rule of thumb for atmospheric pressure?

Every 5.5km air pressure is reduced by half.

What is the approximate value of atmospheric pressure at the earth‘s surface?

1.013 bar = 1013 mbar = 101‘300 Pa

Vacuum

A space devoid of matter.

Explain how a mercury barometer works.

The air pressure on the right pushes the liquid up into the vacuum. The height og mercury in the barometer rises or sinks with an increasing or decreasing air pressure.

Buoyancy

A force exerted upwards by the liquid.

Archimedes‘ principle

An immersed object is buoyed up by a force equal to the weight of the fluid it displaces.

When does a submerged object sink or rise in a liquid.

An object submerged in water is subject to the gravitational force (down) and the buoyant force. Depending on how those two forces compare, the object will sink, hover at constant altitiude, or rise until it floats.

When does an object float?

Only the immersed part of the object‘s volume causes a buoyant force. It is immersed as deep as needed to produce a buoyant force which is equal to the gravitational force.