pressure and moments - physics revision Flashcards
what is the moment?
the turning effect of a force
what does a moment depend on?
- the size of the force
- the distance from the pivot to where the force is
what are moments measured in?
newton metres / centimetres but newton metres are preferred
what is the principle of moments?
if a beam is on a balance with a ‘moment’ on either side, when the beam balances, it creates an equilibrium
anticlockwise moment = clockwise moment
what is the calculation for the moment of a force?
force x distance from pivot
what is the equation two calculate pressure?
pressure ( N/m² or Pa pascal) = force (N)
———–
area (m²)
what happens to the force and pressure when an item has less surface area, such as a bag with thin straps?
the force will be more concentrated and therefore there would be more pressure on your shoulders
what happens to the force and pressure when an item has more surface area, such as a wheelbarrow with many wheels?
as there is more surface area, the force is more spread out, so there is less pressure on the wheels, so the wheels won’t sink into the garden
what is pressure?
a measure of how much force there is per unit area
how do air particles cause pressure?
air particles move about and collide with surfaces. collisions exert force on the surface area which gives you a pressure
what would happen if there is a flame inside a flask, with an egg fitting perfectly in the opening?
the flame uses up the oxygen so the pressure is low inside, and the high pressure outside pushes the egg inside of the flask
how do objects float?
due to the increased pressure of the bottom of an object compared to the top (in water), an upward force is created, causing the object to float
how do objects sink?
if the object is too heavy, it will sink
is pressure the same in all directions?
yes
what effects pressure in water?
where you are - height/depth
- density of the liquid
- gravity pulling down on the liquid
what is the equation for pressure difference?
height x density x gravitational field strength
what are force multipliers?
levers are force multipliers and by exerting the force from further away, it is magnified to make the job easier
example - using a knife to open a paint jar gives a large distance (the knife), but a small force is being used to push it down
what are distance multipliers?
a distance multiplier increases the distance a force is applied to
this works for cogs as when one cog moves so do all the others since they all slot in between one another
what happens to air pressure the higher you get?
the air pressure gets higher
what does pressure increase with?
pressure increases with depth because of the greater weight of water/air pressing down
