Wildcard 1
Wildcard 2
Fluids
Pressure
Cohesion, Adhesion, Flow
100
Why can’t we see through walls?
We see the photons emitted by electron energy level jumps, not physical objects. Our eyes have a sample rate where they calculate photons for a time, then produce an image.
100
What element is the most common in air?
Nitrogen, it’s about 70%.
100
Define a fluid.
Any substance that does not resist shear forces.
100
What are the standard SI Units of pressure?
Pascals
100
What is adhesion
The affinity of a substance to stick to another substance.
200
Do you feel your own weight?
No, you feel the force of the world pushing upwards on your feet.
200
Which freezes faster, hot water or cold water?
Sometimes hot water, but that’s not always true.
200
What is the gauge pressure under 1m of water?
9811Pa
200
What are the base SI units of pressure?
(kg)/(ms^2)
200
What is cohesion?
The affinity of a substance to stick to itself.
300
How far are you from Earth right now?
One radius of Earth, 6378km.
300
What is the average depth of the Pacific Ocean?
4280 meters
300
The magnitude of the buoyant force is equal to...
... the weight of displaced water.
300
How many pascals is 1atm?
101325 Pa
300
When is capillary action stronger, in a narrow tube or a wide tube?
In a narrow tube.
400
Where does sound travel faster, in the air or in water?
It’s much faster in water. In air 
, in water 
.
400
Why are sunsets red?
Earth’s atmosphere blocks more blue light than right light, so if the light passes through more atmosphere, it looks redder.
400
Under what depth of Mercury would the pressure equal
1.1*10^8 Pa?
density Hg = 13700kg/m^3
818m (compare that to 11000m depth of the Mariana Trench)
400
How much force must you apply to a piston to lift a 1500kg vehicle if the piston area at the vehicle is 4x the area you're exerting the force on?
3679N
400
What is the pressure difference on the inside of a water bubble of radius 1cm?
30.24 Pa
500
Are the atoms in your feet touching the atoms in the floor?
No, they’re separated by about 0.5nm due to electric repulsion.
500
Why do bubbles pop?
The internal pressure inside of the bubble is higher than the outside air due to surface tension. If there is a small hole in the thin film, the air escapes.
500
What is the average density of a container ship if 30% of it was submerged in seawater?
717.5 (kg)/m^3
500
How much does the pressure drop from 1atm if the air is moving at a velocity of 230 m/s and the air has a density of
0.27kg/m^3?
7141 Pa
500
How does the velocity of a fluid change if it goes into 2 tubes that are each 1/4 of the radius of the first tube?
The velocity would increase by 8x.