P11 - Force and Pressure Flashcards
(23 cards)
What are examples of fluids?
Liquid or a gas
What is the equation that links area, force normal to a surface and pressure?
pressure=force normal to surface/area
What is the equation that links area, force normal to a surface and pressure?
A force normal(at right angles)
What is the unit for pressure?
Pascals, Pa
What is the unit for force?
Newtons, N
What is the unit for area?
Metres squared, m^2
What equation is used to calculate pressure due to a column of liquid?
Pressure=height of column * density of liquid * gravitational field strength
What is the unit for height of column?
Metres, m
What is the unit for density?
Kilograms per metre cubed, kg/m^3
Why in a liquid, does pressure at a point increase with the height of the column of a liquid above that point and the density of the liquid?
- Collisions give rise to pressure
- so a higher density means a higher pressure
- as the depth of a liquid increases there is more particles above this
- which means the weight of these is on top of the liquid
How is upthrust generated?
A submerged object experiences a greater pressure on the bottom of the surface than on the top, this generates a resultant force upwards
What factors influence floating and sinking?
- Density relative to the fluid and the forces acting on it like weight(downward force) and upthrust(upward force)
What needs to happen for an object to sink?
- If the object’s density is greater than the fluid’s
- If upthrust is less than the weight
What is the atmosphere?
A thin layer of gas around the Earth
What happens to the atmosphere when altitude increases?
Gets less dense
What creates atmospheric pressure?
Air molecules colliding with a surface
What is altitude?
The height of the surface above ground level
What is the number of air molecules representing?
The weight of air
Why does atmospheric pressure decreases as altitude increases?
- The number of air molecules above a surface decrease as height increases
- There is less air above a surface which causes pressure to decrease
What is the value for atmospheric pressure?
30kPa
Identify and explain what happens to pressure with increasing altitude
- As altitude increases, pressure decreases
- Air molecules colliding with a surface create pressure
- As altitude increases the distance between molecules increases so at a higher altitude there are fewer molecules meaning the number of collisions with a surface decrease
What happens to pressure with increasing depth?
- As depth increases, pressure increases
- Increasing depth increases the height of the water above which increases the force of water from above
How does upthrust occur?(3)
- An object that is in water will experience more pressure at the bottom than at the top
- Part of the boat that is deeper under water will have a greater height of water above it exerting a force
- Difference in pressure creates a resultant force called upthrust
