Pressure

Frage	Antworten
Whats the equation for pressure?	Pressure = Force/Area
What is the unit for pressure?	The unit for pressure is the pascal (Pa) which is equivalent to 1N/m2
What is Pressure?	Pressure is force per unit area
What is the link between surface area and pressure?	The larger the surface area, the smaller the pressure. The smaller the surface area, the larger the pressure
Why does a sharp knife cut more easily than a blunt knife?	Because a sharp knife has a much smaller surface/contact area than a blunt knife so there is more pressure on the surface!
What can pressure be transmitted through?	A fluid. For example water or oil
How is pressure used in a hydraulic system?	A hydraulic system uses the pressure in a fluid(oil) to exert a force on an object (the load)
What does the force exerted by a hydraulic system depend upon?	The force exerted by a hydraulic system depends upon the amount of pressure on the cylinder and the area of the cylinder that exerts the force
In terms of hydraulics what is 'F1'?	In a hydraulic system the force F1 is a force created by the moving lever and acting on the narrow, fluid filled cylinder.
In terms of hydraulics what is 'A1'?	After F1 is created it creates a pressure p=F1/A1 on the fluid filled cylinder, where A1 is the area of the narrow cylinder
In terms of hydraulics what happens after the force F1 has been exerted into the cylinder?	Once the force F1 has been exerted, the pressure that was created is transmitted through the fluid in the pipe to a wider cylinder?
In terms of hydraulics what happens after the pressure is transmitted through the pipe into the wider cylinder?	The force on the larger piston, F2, is created by the pressure that is transmitted into the wider cylinder.
In terms of hydraulics what is 'F2' and 'A2'?	F2 is the force on the larger piston, F2 = p x A2, where A2 is the area of the wide cylinder.
In a hydraulic system, what is the equation to work out the value of the force acting on the larger piston (F2)?	F2= F1/A1 x A2
How does the pressure in a liquid increase?	Pressure in a liquid increases with an increase of depth and an increase in density.
What is the equation for the volume of a liquid in a container?	The equation is for a column of height 'h' and area of cross-section 'A', the volume of the liquid in the container = hA
What is the equation for the mass of liquid?	The mass of liquid = its volume (hA) x density of the liquid (p) = hAp
What is the equation for a weight of the liquid?	The weight of the liquid = mass x gravitational field strength (g) = hAp x g. Where g (gravitational field strength) = 10 N/kg
What is the equations and workings for the pressure at the base of the liquid column?	Pressure 'P' at the base of the liquid column = weight/area of cross-section =hApg/A and canceling the 'A' out gives P=hpg
What is the difference in water flow between a bottle with 4 holes at different depths and a bottle with 4 holes all at the lowest but the same depth?	The bottle with 4 holes at different depths will have a slower water flow because the top 3 holes are under not very much pressure, whereas the bottle with 4 holes all at the same depth will have a faster water flow as they are under greater pressure
What is a U-tube manometer used for?	A U-tube manometer is used to measure pressure in a gas.
What is a mercury barometer used for?	A mercury barometer is used to measure atmospheric pressure.
In a mercury barometer what happens if there is an increase in atmospheric pressure?	An increase of atmospheric pressure causes the mercury to rise up inside the tube.
In a mercury barometer what happens if you see the mercury level falling?	If the mercury level is falling then there has been a decrease in atmospheric pressure.
What happens to atmospheric pressure above sea level?	Atmospheric pressure decreases with height above sea level. The cabins of aeroplanes that fly at high altitudes are pressurized to be at 'sea level' pressure so the occupants can breathe normally.
What is the mean value of the atmospheric pressure at sea level?	The mean value of atmospheric pressure at sea level is 101 kPa, which is referred to as standard atmospheric pressure and it corresponds to a height of 760mm for the mercury column in a barometer.
What are the molecules like in a solid?	The molecules in a solid are in a rigid structure
What are the molecules in a liquid like?	The molecules in a liquid move about in contact with each other
What are gas molecules like?	Molecules in a gas are far apart and move around at a high speed.
Do solids and liquids have a higher density than a gas?	Yes they do
What is the density of water?	1
What are the processes called when a liquid turns to a gas?	The processes in which a liquid changes state into a gas are called boiling or vaporisation.
What is the process in which a gas turns to a solid or a liquid?	Condensation
What is it called when a solid changes state into a gas?	Sublimation
What are the processes when a liquid turns to a solid and when a solid turns into a liquid?	A liquid to a solid is called freezing or solidifying. And a solid to a liquid is called melting.
What happens when you increase the temperature of a gas?	You are increasing the average speed of its molecules.
How is the pressure of a gas on a surface caused?	The pressure of a gas on a surface is caused by its molecules repeatedly hitting the surface.
What happens to the pressure of a gas in a sealed container is the gas temperature is increased?	The pressure increases
What is Brownian motion?	Brownian motion is the erratic motion of microscopic particles, due to random impacts of gas molecules on each particle.
What does evaporation from a liquid occur as a result from?	Evaporation from a liquid occurs as a result of molecules with sufficient kinetic energy leaving the liquid.
How can evaporation from a liquid be increased?	It can be increased by increasing the temperature or surface area of the liquid or by creating a draught of air across its surface.
For a fixed mass of gas at a constant temperature, what happens when its volume is decreased?	Its molecules hit the surfaces of its container more often; its pressure increases and its pressure x its volume is constant.

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