Physics: October 2011

Monday, October 31, 2011

5.9 and 5.10

5.9 and 5.10 starter

28 October 2011

12:01

Tell the person next to you…

· How do particles in move in a solid, a liquid and a gas?

· Describe…

o speed of particles

o relative position of particles (fixed or not)

o pattern of particles (regularly arranged or not)

o size of the particles

o space between the particles

o strength of bonds between the particles



			Use the animation to verify your answers

5.9 and 5.10

28 October 2011

10:21

· 5.9 recall that particles in a liquid have a random motion within a close-packed irregular structure

· 5.10 recall that particles in a solid vibrate about fixed positions within a close-packed regular structure

· Complete the missing words in the table below

· Cut and paste the particle images into the table

State

Particle

Picture

Arrangement of Particles

Motion of Particles

Other Properties

Solid

· closely packed

· regular position

· vibrate about a fixed position

· fixed shape

· not easily compressed since particles are closely packed

· Strong bonds

Liquid

· closely packed

· no position

· free to flow over each other

· takes shape of its container

Thursday, October 27, 2011

5.6

5.6 recall and use the relationship for pressure difference:

pressure difference = height × density × g

∆p = h × ρ × g

∆p = pressure of the fluid (N/m² or Pa)

h = height of the fluid (m)

ρ = density of the fluid (kg/m³)

g = gravitational field strength (N/kg)

5.6 Demo - squirting water column

12 October 2011

07:24

· The bottom hole squirts water the furthest

· Because the water at the bottom has the greatest pressure

· Because in the formula ∆p = h × ρ × g, ρ is constant, g is constant and h is large

· So ∆p = large

5.6 Questions

07 October 2011

11:53

Collins, p.107

Q.5)

pressure difference=height*density*g

(250 000-100 000)=x*1000*10

150 000/10 000=x

15m=x (height)

Yes, because fresh water is denser then fresh water, therefore increasing the answer slightly

Q.6)

P=h*p*g

(1600 mbar=160 000Pa)

160 000-x=50*0.42*1.4

x=29.4

Total pressure

=29.4+160 000

Correction

0.42cm3=420m3

50*450*1.4

=29 400

Total Pressure

=29 400+160 000

=189,000Pa

DONT FORGET TO CHECK UNITS!!!!!!!!!!!!!!

Notes:

ρ_{fresh water} = 1,000kg/m³

g = 10N/kg

1,000mbar = 1 bar = 100,000Pa

5.6 Plenary

12 October 2011

07:23

· Which diver experiences the greatest pressure?

5.5

· 5.5 understand that the pressure at a point in a gas or liquid which is at rest acts equally in all directions

5.5 Demo 1 - Magdeburg Hemispheres

12 October 2011

07:19

· Magdeburg Hemispheres

· The original experiment was done by using two teams of wild horses to try and pull the hemispheres apart

· And here are the horses I was talking about!

5.5 Demo 2 - Collapsing Bottle

12 October 2011

07:19

· Collapsing Bottle

Objective 5.4

5.4 Starter 2 explained

07 October 2011

09:04

<<animation - why a drawing pin works.swf>>

· Your finger pushes on the pin and the pin pushes back on your finger

· N3L tells us that all these two forces are equal in size

· The pin pushes on the wall and the wall pushes back on the pin

· N3L tells us that all these two forces are also equal in size

· If the surface area is large then the force is spread over a large area and the pressure is low

· If the surface area is small then the force is spread over a small area and the pressure is high

· You would like the pressure on your finger to be low and the pressure on the wall to be high

· The other way round is painful!

5.4

07 October 2011

10:37

· 5.4 recall and use the relationship between pressure, force and area:

pressure = force / area

p = F / A

5.4 Pressure Questions

07 October 2011

11:47

· PFY p.91, Q.3 and 7.

Pressure=Force/A

100000=F/10

100000*10=F

1 000 000N=F

A) P=F/A

P=500/5

P=100N/m2

B) F=P*A

F=100*20

F=2000N

1) Snow shoes have a large SA,

so there is less pressure

therefore they don’t sink in the snow when they walk

2) Large A

Less pressure

Enables them to go through mud without sinking/getting stuck

Also, as they are used on farms,

it enables them to roll over objects such as potholes easier without bursting a tire

animation - why a drawing pin works.swf Download this file

Saturday, October 15, 2011

Harder density questions

Eliza de Vries 11B

:) :) )

Sunday, October 9, 2011

Density Questions

P5 keywords

5.2

Density formula.ppt Download this file

5.2 recall and use the relationship between density, mass and volume:

density = mass / volume

ρ = m / V

5.3 Plenary

Drag'n'Drop Density (in kg per m3).swf Download this file

Remember: 1g/cm³ = 1,000kg/m³

5.3 Density of a regular solid, irregular solid, liquid

Density Practical - regular and irregular solids and liquids.ppt Download this file

Eliza de Vries 11B

:) :) )

5.3 describe how to determine density using direct measurements of mass and volume

Density Practical - regular and irregular solids and liquids.ppt Download this file

5.3 describe how to determine density using direct measurements of mass and volume

Saturday, October 8, 2011

Untitled

Eliza de Vries 11B

:) :) )

Tuesday, October 4, 2011

Untitled

Eliza de Vries 10S