We want to solve for H v : Fill in variables from data table; H v will be the unknown.

We want to solve for Hv:

Fill in variables from data table; Hv will be the unknown

Heat of Vaporization Lab

0

0

0

TmcmHTmcTmc

QQQQ

QQ

v

atercondensedwwatersteamrcalorimetewater

lostgained

To calculate percent error:

Where accepted is 2.26x106 J/kgC

Percent error:

acceptedH

acceptedHcalculatedHerror

V

VV %

VH

1.What does the word “fluid” mean to you?

2.List 5 examples of fluids

3.What does the word “pressure” mean to you?

Do Now (3/8/12):

1.What principle describes the buoyant force?

2.What is a fluid?3.What principle

describes pressure in a fluid?

Do Now (5/31/12):

Exam Review: Please use the rest of class to work on your

review packet. Not working on your packet will result in a

loss of 2 points for today!!! If you have any questions or need any

slides, please ask.

Fluids and Pressure

Fluid: materials that flow and have no definite shape of their own

Fluids

F=forceA=area

Measured in Pascals (Pa)

Pressure: the force on a surface

A

FP

211m

NPa

What animal do you think exerts the greatest pressure on the earth?

Brainstorm:

A pig!!!

A child weighing 364 N stands on the ground. His feet take up an area of 0.2 m2. What pressure does he exert on the ground?

Example #1:

A child of mass 45 kg sits on a 5 kg 3 legged stool whose legs take up an area of 20 cm2. a.What is the pressure

exerted by the child and the stool?

b.If the child leans on two legs, what is the new pressure?

Example #2:

1. Use the rest of class to work on your homework: Density and Pascal’s Principle. It is due on Monday!

Practice:

1. Use the rest of class to work on practice problems 1-2 on page 303 of your classroom textbook

2. If you finish, work on your lab3. A-Course: Problems 1-5 on p. 344 of home

textbook4. B-Course: Problems 1,2,3,5 on p. 344 of

home textbook – due Wed 3/16

Practice:

Strategies:

Review: Pressure

A

mg

A

F

A

FP g

Density: the amount of mass per unit volume

ρ=(rho) density m=mass V=volume

Review: Density

V

m

The density of brass is 8.4 g/cm3. What is the approximate volume of a 800-g brass monkey?

Example:

A child exerts 4000 Pa of pressure on the ground. His feet take up an area of 0.2 m2.

1.What is his weight? 2.What is his mass?

Do Now (3/9/12): HAPPY FRIDAY!!!

The air pressure exerted on Earth at sea level; 1 atm = 105 Pa or 100 kPA

Atmospheric Pressure

Any change in pressure applied at any point on a confined fluid is transmitted undiminished throughout the entire fluid

Think of squeezing toothpaste out of a tube!

Pascal’s Principle

a hydraulic apparatus used to lift or move objects using the force created when pressure is exerted on liquid in a piston

Hydraulic Lift

Pascal’s Principle:

Force exerted by a hydraulic lift:

Hydraulic Lift

1

212 A

AFF

2

2

1

1

21

A

F

A

F

PP

In a machine shop, a hydraulic lift is used to raise heavy equipment for repairs. The system has a small piston with a cross sectional area of 0.01 m2 and a large piston with cross sectional area of 0.20 m2. How much load can be lifted by the large piston if 150 N of force is exerted into the small piston?

Example:

Please use the rest of class to finish your homework.

If you finish your homework, please meet with your mousetrap car group!!

Mousetrap cars need to be built by MONDAY MARCH 19

Practice:

The input piston of a hydraulic lift is 0.2 m in diameter, and the output piston is 0.1 m in diameter. How much output force will an input force of 4 N produce?

Do Now (3/12/12):

Absorption of heat causes an increase in length; release of heat causes a decrease

Linear Expansion

Linear Expansion

L= length ΔL=change in length ΔT= change in temperature αL= coefficient of linear expansion

The degree of expansion divided by the change in temperature for each material

Coefficient of Linear Expansion

A copper pipe is 100 meters long at 5oC. The pipe is heated to 105oC. The coefficient of linear expansion for copper is 2.0 x 10-5 / oC. What is the change in length of the copper pipe? 

Example:

You have the rest of class to work on your pre-labs. They are due at the end of class!!!

Once you finish, get together with your group and work on your mousetrap car. It is due NEXT Monday, 3/19!!!

Pre-Lab

Accepted Linear Expansion Values of Common Materials

Material a(x10-5 °C-1) Glass (ordinary) 0.09 Glass (Pyrex) 0.32 Concrete 1.20 Steel 1.24 Copper 1.76 Aluminum 2.34 Lead 2.90

1.What is a Bunsen burner?

2.How does it work?3.What are some good

safety guidelines to keep in mind when working with Bunsen burners?

Do Now (3/13/12):

The Forth railway bridge has an overall length of 2,529 m (about 1½ miles). It is made of steel (coefficient of linear expansion = 0.000012 per °C). If the greatest difference in temperature between the coldest and hottest days is 35°C what is greatest the length the bridge can change by?

Do Now:

1.What is the pressure on the ground of a 4 kg brick whose bottom is 0.3 m long and 0.2 m wide?

2. Turn in homework and Do Now’s

Do Now:

Should be completely DESIGNED by Monday!!! If you have already built yours, then you are ahead of the game

Mousetrap cars

Get together with a group of 3-4 people to design a boat based on the specifications on your paper. Your drawing should include specific designs and measurements!!! When you are finished, check in with me.

Archimedes Boat

Take out your boat design. Discuss your reasoning with your neighbor and list two reasons for your boat’s shape.

Do Now (3/15/12):

1. What is Archimedes Principle?

2. How did it relate to yesterday’s lab?

Do Now:

How well did your boat do yesterday? What design decisions do you think caused your success or lack thereof?

Do Now (3/16/12):

An object immersed in a fluid has an upward force on it equal to the weight of the fluid displaced by the object

ρfluid=density of the fluid V=volume of object g=9.8

Archimedes’ Principle

VgF fluidbuoyant

A cubic decimeter (1x10-3m3) of a granite building block is submerged in water. The density of granite is 2.7x103kg/m3. the density of water is 1000 kg/m^3◦What is the buoyant force acting on the block?

Example

Less dense materials FLOAT when mixed with more dense materials

More dense materials SINK when mixed with less dense materials

Buoyant Force

Density: kg/m3

Mass: kgVolume: m3

If your units are not in these, you must convert!!!

Units

Use the rest of class to work on the paper Archimedes Principle. It will be due next week!!!

You will also have a test next week!!!

Practice:

1. Think back to our unit on energy. What type of energy do you think a mousetrap has before it is sprung?

2. What is the area of the trapezoid?

Do Now (3/19/12):

0 0.02 0.04 0.06 0.08 0.1 0.12 0.140

2

4

6

8

10

12

DISTANCE (Meters)

FO

RC

E (

New

ton

s)

The area under the curve of a Force-distance graph is the potential energy!

Mousetrap Lab:

Pass in final car designs and Boat Labs, then head over to room 127.

Mousetrap Lab:

1.What is the buoyant force exerted on a steel object with volume 2x10-3 m3 floating in crude oil? The density of crude oil is 900 kg/m3 and the density of steel is 7850 kg/m3.

Do Now (3/20/12):

A gold crown (density is 19,300 kg/m3) weighs 40 N in air.

1. What is the volume of the crown?

2. What is the buoyant force of the crown?

3. What will it weigh when suspended in crude oil whose density is 900 kg/m3?

Practice Problem:

Use the rest of class to work on the paper Archimedes Principle. It is due tomorrow!!!

Mousetrap labs are due Friday!!! Come in tomorrow with any questions about the lab!!!

Practice:

A gold crown (density is 19,300 kg/m3) weighs 20 N in air.

1. What is mass of the crown?2. What is the volume of the

crown?3. What is the buoyant force of

the crown when suspended in sunflower oil whose density is 920 kg/m3??

Do Now (3/21/12):

Pass in homework, then leave your things and walk over QUIETLY to room 127.

Pass in:

Apparent weight: The weight in a given frame of reference

Apparent Weight

buoyantgapparent FFF

A cubic decimeter (1x10-3m3) of a granite building block is submerged in water. The density of granite is 2.7x103kg/m3.◦ What is the buoyant force acting on the block?

(9.8N)◦ What is the apparent weight?

Example

Clear your desks of everything except a blank sheet of paper and a writing utensil

A cubic decimeter (1x10-3m3) of a granite building block is submerged in water. The density of granite is 2.7x103kg/m3.◦What is the buoyant force acting on the block?

◦What is the apparent weight?

Pop Quiz:

1. What is the buoyant force exerted on a steel object with volume 2x10-3 m3 floating in crude oil? The density of crude oil is 900 kg/m3 and the density of steel is 7850 kg/m3.

2. What is the apparent weight?

Do Now:

A steel crown (density is 7850 kg/m3) weighs 40 N in air. What will it weigh when suspended in sunflower oil whose density is 920 kg/m3?

Pop Quiz: