P1.3 Flashcards
what is the unit used for pressure
Pascal (Pa)
describe the motion of molecules in a gas
they are in constant random motion
how can the pressure of a gas be increased whilst kept at constant temperature
the volume can be decreased
how can the pressure of a gas be decreased whilst kept at constant temperature
the volume can be increased
what effect does increasing temperature have on the pressure of a gas when held at constant volume
pressure of the gas will increase and the temperature increases
why does pressure increase as temperature increases ( at a constant volume)
kinetic energy of molecules increases
collisions between molecules becomes more frequent
greater rate of change of momentum
greater force and therefore pressure
if gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?
there are more collisions per second in gas B than in gas A
the rate of collisions is higher in B
describe the force that that pressure of a gas exerts on the walls of its container
the net force acts at right-angles to the container’s surface
the magnitude of the force increases as pressure increases
explain how increasing the volume of a gas results in a decrease of pressure
molecules become more spread out so collisions become less frequent
rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure
what can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?
it is constant
p V = constant
what increases when you do work on a gas?
the internal energy of the gas
this can also lead to an increase of temperature
why does the temperature of air inside a bike pump increase when it is pumped?
work is done on a gas when it is compressed
doing work on gas increases its internal energy, so also increases the average kinetic energy of the molecules
temperature increases with an increase of average kinetic energy
why does atmospheric pressure decrease as you move higher above the earth’s surface
the atmospheric pressure at a point is equal to the weight of the air in the column above that point, as you move higher above the Earth the amount of air in said column decreases - resulting in less weight above and as a result less pressure at the point
what does an object in a fluid experience as a result of pressure
forces at right angles to all of its surfaces
pressure in a fluid _____ with depth. Why?
increases, because it is caused by the gravitational force on the fluid above that point. The deeper you go, the greater the weight of water above you, and so a higher force and pressure.
what equation is used to calculate pressure at a given depth of liquid
pressure = depth x liquid density x gravitational field strength
what is upthrust
the upwards force that an object experiences in a fluid as a result of a greater pressure below the object than above it
under what circumstances will an object float?
when the object’s upthrust equals its weight
under what circumstances will an object sink?
when the object’s upthrust is less than its weight
when you submerge an object in a liquid, what is the upthrust acting on the object equal to?
the weight of the volume of liquid displaced as it is submerged
what can be said about the density of an object that sinks in water?
the object’s density is greater than the density of water.
