Mechanics - Pressure & Flotation Flashcards
Define Density and give (i) unit and (ii) equation.
The density of a substance is its mass per unit volume.
kg/m^3
p=m/v
Define pressure and give (i) unite and (ii) equation.
Pressure is force per unit area.
Pa // N/m^3
p=f/a
There is immense amount of mass (900kg) of the atmospheric gas column.
How come we don’t get crushed down by this mass?
The gas is balanced by an equal opposing pressure from within your body.
Differentiate the two different types of pressure: (i) high (ii) low
High pressure: summer dry fine weather & frosty winter night
Low pressure: wet, windy & cloudy weather.
Define Boyle’s Law.
The volume of a fixed mass of gas is inversely proportional to its pressure, as long as temperature remains constant.
Express the relationship between pressure and volume when it’s inversely proportional. [use examples]
pressure 1/2 = volume 2
pressure 3 = volume 1/3
Express the equation for Boyle’s Law.
p1 v1 = p2 v2
‘The pressure at the bottom of the dam’
‘is higher than the top of the dam.’
Define hydrostatic
Pressure due to a liquid
Give the traits of hydrostatic
- Acts on all bodies in the fluid.
- Act in all the same directions at a given depth.
- Hydrostatic pressure increases as depth increases.
- Acts in a perpendicular direction to all surfaces immersed in the liquid.
Define absolute pressure and give its equation
Atmospheric pressure and hydrostatic pressure combined.
P = ‘rho’gh
What’s a hydrometer?
An instrument used to gauge density of liquids. The higher the liquid’s density, the higher the hydrometer floats in the liquid.
What are the uses of the hydrometer?
- Check for fraud in the alcohol and dairy industries.
- If the hydrometer does not sit right = liquid is tampered.
What is Archimedes’ Principle?
Whenever an object is totally or partially immersed in a fluid, it experiences an upthrust that is equal to the weight of the fluid it displaces // Upward force = upthrust or buoyancy.
Define Law of Flotation
Whenever an object is floating, the weight of the fluid displaced will equal the object’s weight.
