# 5 Pressure and Density Flashcards

1
Q

Define density

A

the mass per unit volume

2
Q

How do you measure volume accurately when using a measuring cylinder?

A

Read the volume at eye level and to the bottom of the meniscus

place measuring cylinder on a level surface

3
Q

What is the unit for density?

A

g/cm3 or kg/m3

4
Q

Which orientation of the block below would create in a smaller pressure on a table?

A

First orientation

P = F/A

The second block has a larger area in contact with the table, for the same force, therefore, the pressure is lower

5
Q

How can the volume of an irregular object be found using a measuring cylinder?

A
1. Half fill measuring cylinder with water and read initial volume at eye level and bottom of the meniscus
2. lower object into measuring cylinder- make sure that it is fully submerged and water level has not risen above the scale
3. read final volume at eye level and bottom of the meniscus
4. Volume of object = final volume - initial volume
6
Q

The second object has half the mass but the same volume, How does its density compare to the first object?

A

density = mass / volume

if mass is double for the same volume, the density doubles.

density is proportional to mass

7
Q

How could you find the density of a paperclip accurately?

A
1. measure the mass of 50 paperclips on a balance
2. half fill a measuring cylinder with water and record initial volume
3. carefully add 50 paperclips and record final volume.
4. calculate the volume by taking the difference
5. Find density = mass / volume
8
Q

What is a pascal?

A

1 Pascal = 1 Newton per metre square

9
Q

How do you find the density from a mass vs volume graph?

A

gradient = rise/run = mass/volume

10
Q

Explain what design feature makes a knife able to cut easily.

A

A sharp knife with a small surface area creates a greater pressure for the same force.

pressure = force/area

The knife will cut more easily

11
Q

What equation links density, mass and volume?

A
12
Q

What is the unit for force?

A

Newton or N

13
Q

Camels have adapted to walk effortlessly in the desert sand. Explain

A

Camels feet have a large surface area

P = F/A

A larger surface area for the same force results in lower pressure

The camel will not sink as much in the sand and can walk more easily.

14
Q

How can the volume of an irregular object be measured accurately using a Eureka can?

A
1. overfill eureka can with water and wait for water to stop dripping from the spout
2. hang object from a string and slowly lower the object into the water
3. make sure that the object is fully submerged
15
Q

Which orientation of the block below would create a larger pressure on a table?

A

Second orientation

P = F/A

The second block has a smaller area in contact with the table for the same force, therefore, the pressure is higher

16
Q

What is the unit for volume?

A

m3

17
Q

If a block of wood is cut in half, how does the density of the original block compare with the new half blocks?

A

Their densities are the same.

Both the mass and the volume were halved.

18
Q

Which dam must withstand a larger pressure?

A

The pressure on both dams is the same since the depth of water is the same

19
Q

What is the unit for pressure?

A

Pascal (Pa)

20
Q

What is the equation that links pressure, density of a fluid, gravity and depth?

A
21
Q

Which section A, B, C, D or E experiences the largest pressure?

A

P = density x gravity x depth

All the sesctions experience the same pressure since the depth of water is the same.

Pressure at depth is not affected by the volume of water- only the depth of water above it.

22
Q

How does the density vary between ice and sea water?

A

Ice has less particles per unit volume

ice has a lower density

Ice floats on sea water

23
Q

How can mass be measured accurately?

A
• placed balance on level surface
• tare (zero) balance before use
24
Q

How does the pressure vary with depth in the ocean?

A

As depth double, pressure doubles.

Pressure is proportional to depth

The graph is a straight line through the origin.

25
Q

What is the unit for mass?

A

kg

always convert grams to kilograms

26
Q

Fluid pressure acts in all directions.

What causes air pressure?

A

Air particles move in all directions and collide with objects

Air particles move fast and freely

Air pressure is related to the depth of air over the object.

27
Q

What is the unit for area?

A

m2 or cm2

28
Q

What equation links pressure, force and area?

A
29
Q

Which object (a or b) has the largest density?

A

Object a

It has more mass per unit volume - the gradient is steeper

30
Q

Which object below would have the highest density values?

A

First object

Greater mass per unit volume

The particles are more closely packed