forces and matter - topic 14 Flashcards
what is pressure
a force exerted normal (90 degrees) to a surface per unit area of that surface
pressure =
force / area
what is a fluid
a substance that can flow like a gas or liquid
the denser the fluid or deeper the point you are looking at
the higher the fluid pressure
total pressure at a point in a fluid =
the sum of the pressure due to the fluid itself and surrounding atmospheric pressure
the denser the liquid ……
more particles in a given volume and more collisions so higher force exerted so higher pressure
as depth increases
number of particles above that point increases and the weight of these particles adds to the pressure experienced
liquid pressure =
height x density x gravitational field strength
how it atmospheric pressure created
created on a surface by air molecules colliding with the surface
as altitude increases,
atmospheric pressure decreases
as altitude increases,
atmosphere gets less dense and fewer air molecules that are able to collide with a surface which means lower atmospheric pressure
upthrust =
weight of displaced fluid
what happens to the force as pressure increases with depth,
force exerted on bottom of object is larger than the force acting on the top of it
if upthrust = objects weight
object will float
if object weighs more than upthrust
it sinks
objects that is more dense than the fluid it is in
is unable to displace enough fluid to equal its weight and will sink as weight is larger than upthrust
in order for an object to be stretched, compressed or bend
more than one force needs to be acting on an object in different directions
elastically distorted
able to go back to their original shapes and lengths once the force has been removed
inelastically distorted
unable to return to their original shapes and lengths once the force has been removed
relationship between force and extension
force is directly proportional to extension
force =
Spring constant x Extension
limit of proportionality
the point beyond which the force applied to an elastic object is no longer directly proportional to the extension of the object
elastic limit
the maximum force that can be applied to an object before it is permanently distorted
work done
is when a force stretches or compresses an object and causes energy transfer
what happens to an objects energy if object is elastically distorted
all energy is transferred to the objects elastic potential store
energy transferred in stretching =
0.5 x spring constant x extension^2
investigating springs
- measure natural length of the spring with ruler
- add mass to spring and allow it to come to rest
- measure new length and record weight
- E = 0.5 X k X x^2
- repeat and plot results graph
what is hooke’s law
The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
how is pressure related to force and area
if a person is wearing high heels, their weight(force) acts on the ground over a very small area. This causes a large pressure on the ground.
why does atmospheric pressure decrease as height above earth increase
as altitude increases, atmosphere gets less dense which means there are fewer air particles able to collide with a surface so lower atm
as altitude increases, there are fewer air particles above a surface so weight above the air decreases
