Density and Pressure Flashcards
Why are some objects denser than others?
The more closely the particles in an object are packed, the denser the object and/or the particles in the object have a large mass.
What is the formula for density?
Density=mass÷volume
How can you work out the volume of something when you know the mass and density?
Volume=mass÷density
How can you work out the mass of something when you know the volume and density?
Mass=volume×density
A piece of metal has a mass of 1350kg and a volume of 0.5m cubed. What is the density of the metal?
2700kg/m cubed
What are all the correct units for density?
g/cm cubed, kg/m cubed, kg/L, g/ml
Why do some objects float in liquids?
Objects float if they are less dense than the surrounding fluid. They will sink if their density is higher than the surrounding fluid.
How would you measure the density of a regular solid?
Find the mass using a balance.
Measure the length, width and breadth using a ruler.
Multiply these together to find the volume.
Calculate the density by dividing the mass by the volume.
How would you find the density of an irregular solid?
Find the mass using a balance.
Fill a measuring cylinder up to a known volume (e.g. 50cm cubed)
Put the irregular solid into the water and measure the new volume.
The difference between the known volume and the new volume is the irregular solid’s volume .
Divide the mass by the volume for the density.
How would you find the density of a liquid?
Find the mass of an empty measuring cylinder using a balance.
Pour the liquid in and find the mass of the measuring cylinder with the liquid in it.
The mass of the liquid is the difference between the mass of the empty cylinder and the mass of the measuring cylinder with the liquid in.
Divide the mass by the volume for the density.
What is the formula for pressure?
Pressure=force÷area
How would you work out the force of an object from the pressure and the area?
Force=pressure×area
How would you work out the area from the force and pressure?
Area=force÷pressure
What are all the units for pressure?
N/m squared, N/mm squared, N/cm squared
What is 1Pa (1 pascal) the same as?
1N/m squared
Give an example where pressure is used to concentrate the load. Explain why.
A drawing pin. The part of it that touches a surface has a very small area and the smaller the area, the more pressure.
Give an example where pressure is used to spread load and explain why.
A flat shoe. When a lot of force is put on an object, the pressure becomes higher. When the area of an object is large, even if the force is considerate, the pressure is lower.
What are the 2 states of matter that are fluids?
Liquids, gases
Can fluids exert pressure?
Yes
Which direction does pressure in a fluid act?
All directions.
What happens to the pressure in a fluid as you go deeper? Why is this?
It increases because the deeper you go, the larger mass of the fluid you have over you and the larger the mass, the larger the pressure.
