Note Card QuizNote Card Quiz

Name_____________ Date _____ Period ___

Activity 54, Analysis #3

Major Concepts:Major Concepts:►Activity 56Activity 56

There was a direct relationship between There was a direct relationship between the amount of kinetic energy put into the the amount of kinetic energy put into the system and the amount of energy system and the amount of energy transformed (thermal energy). This was transformed (thermal energy). This was measured by an increased temperature.measured by an increased temperature.

►Activity 58Activity 58 The sun is a major source of energy for The sun is a major source of energy for

changes on earth’s surface.changes on earth’s surface. Energy can be transferred, however, it Energy can be transferred, however, it

can never be destroyed.can never be destroyed.

Major Concepts:Major Concepts:►Activity 73Activity 73

Making decisions often involves trade-Making decisions often involves trade-offs-----giving up one thing to gain offs-----giving up one thing to gain another.another.

The potential for accidents and the The potential for accidents and the existence of hazards impose the need for existence of hazards impose the need for injury prevention and the need to injury prevention and the need to understand the physics of how a car understand the physics of how a car moves (force and motion) moves (force and motion)

What factors can contribute to a What factors can contribute to a car accident?car accident?

SpeedSpeed

►Speeding or going too fastSpeeding or going too fast► In the United States, car speed is In the United States, car speed is

typically measured in mph.typically measured in mph.►km/h is used for car speed in other km/h is used for car speed in other

countries. countries. ►Scientists often measure everyday Scientists often measure everyday

speeds in m/s.speeds in m/s.►Today, we will measure speed in cm/s.Today, we will measure speed in cm/s.

Title:Title: Measuring Speed

Activity 74

Background Information:Background Information:►SpeedSpeed

An object in motion takes time to change its position. Speed is the measurement of the rate of change in position and can be linear or rotational. The units for speed are a distance or an angle per unit of time, such as miles per hour or degrees per second.

►VelocityVelocity Speed (s) and velocity (v) are related

concepts but are not the same thing. The velocity of an object includes both its speed and its direction.

Speed vs. VelocitySpeed vs. Velocity

►What is the difference?What is the difference?

The velocity of an object includes both The velocity of an object includes both its speed and its direction.its speed and its direction.

More vocabularyMore vocabulary►tested variabletested variable: the variable that is : the variable that is

manipulated manipulated (changed) in an (changed) in an experiment. Also called experiment. Also called independentindependent variable.variable.

►controlled variablescontrolled variables: the variables that : the variables that are not changed in an experiment. are not changed in an experiment. 

►responding variableresponding variable: the variable you : the variable you are are measurmeasuring in an experiment. Also ing in an experiment. Also called called dependentdependent variable. variable.

Read E-7Read E-7

Part APart A

Problem:Problem: How can you measure the How can you measure the speed of a moving cart?speed of a moving cart?

Hypothesis Part A:Hypothesis Part A: If you ______________, If you ______________, then you can ______________________.then you can ______________________.

How do people measure How do people measure speed?speed?

►SpeedometerSpeedometer►Radar GunRadar Gun►Total Distance/Total TimeTotal Distance/Total Time

READ THE PROCEDURE!READ THE PROCEDURE!

Level portion of the trackLevel portion of the track

ProcedureProcedure►Step #8 – Why do you use three trials?Step #8 – Why do you use three trials?►Watch for Watch for ERRORERROR. What is this?. What is this?

Timing errors may cause the time to be too Timing errors may cause the time to be too long or too short.long or too short.

You may stop the watch too soon, and You may stop the watch too soon, and sometimes too late. sometimes too late.

Your reaction time may effect the timing.Your reaction time may effect the timing. Taking the average of 3 trials can limit the Taking the average of 3 trials can limit the

error.error. You may need to do an addition trial if one You may need to do an addition trial if one

is too far off from the others.is too far off from the others.

Minimize ErrorsMinimize Errors

►Release the cart the same way each Release the cart the same way each time.time.

►Try to get data that is Try to get data that is ACCURATEACCURATE and and REPRODUCIBLEREPRODUCIBLE..

► If you get 10 cm/s, 11 cm/s, and 25 If you get 10 cm/s, 11 cm/s, and 25 cm/s, you may want to redo the third cm/s, you may want to redo the third trial.trial.

►Put a book to stop the cart. The cart Put a book to stop the cart. The cart SHOULD NOT roll off the table.SHOULD NOT roll off the table.

Data/Evidence:Data/Evidence:

TrialTrial Distance (cm)Distance (cm) Time (s)Time (s) Speed (cm/s)Speed (cm/s)

11 100100

22 100100

33 100100

Always include units

Average

FIX

Speed = Distance/TimeSpeed = Distance/Time

►What is the speed of a car that travelsWhat is the speed of a car that travels 100 miles in 2 hours?100 miles in 2 hours?

►50 MPH50 MPH

►What is the speed of a car that travels What is the speed of a car that travels 30 kilometers in 1/2 hour?30 kilometers in 1/2 hour? 60 km/h60 km/h

Is read “per” and means to divide

Part A DiscussionPart A Discussion►What is a variable?What is a variable?

A variable is what we change, measure A variable is what we change, measure and control in an experiment. They are and control in an experiment. They are the factors that influence the speed of the the factors that influence the speed of the cart.cart.

►What variable did we test?What variable did we test?There was no tested variable. You did not There was no tested variable. You did not change or manipulate any factors.change or manipulate any factors.

►What variables did we control?What variables did we control?the track (release height, angle & surface)the track (release height, angle & surface)the cart’s massthe cart’s mass

Part BPart B

Problem:Problem: What will happen to the speed What will happen to the speed of the cart if we change the release of the cart if we change the release height of the cart?height of the cart?

Hypothesis:Hypothesis: If you lower the release If you lower the release height of the cart, then height of the cart, then ____________________.____________________.

How will you test your How will you test your hypothesis?hypothesis?

How many trials?How many trials?

What are your variables other than What are your variables other than height?height?

How many variables are you changing?How many variables are you changing?

Calculating SpeedCalculating SpeedWhy did we use the “average value”?Why did we use the “average value”?

What does it mean if your data is What does it mean if your data is accurate?accurate?

► the ability to match the actual valuethe ability to match the actual value

What does it mean if your data is What does it mean if your data is reproducible?reproducible?

► precision is the ability of a measurement precision is the ability of a measurement to be consistently reproducedto be consistently reproduced

Why are these qualities important to Why are these qualities important to scientists?scientists?

Calculating SpeedCalculating Speed

Speed = distance traveled / timeSpeed = distance traveled / time

What units did we use in this lab?What units did we use in this lab?

What units would you use to measure the What units would you use to measure the speed a car travels?speed a car travels?

What units would you use to measure the What units would you use to measure the rate at which your hair grows?rate at which your hair grows?

►What was the tested variable?What was the tested variable?

The height of the release of the The height of the release of the cart. This was the variable we cart. This was the variable we changed or manipulated.changed or manipulated.

►What variable was time?What variable was time?►Was there a different controlled Was there a different controlled

variable in part B?variable in part B?

Discuss Analysis 1-3 with your Discuss Analysis 1-3 with your groupgroup

1.1. According to your data from part A, According to your data from part A, what is the speed of the cart?what is the speed of the cart?

2.2. According to your data from part B, According to your data from part B, what is the effect of release height on what is the effect of release height on speed?speed?

3.3. List some common units for speed. List some common units for speed. Why are there so many different units?Why are there so many different units?

We choose units which are We choose units which are both convenient and both convenient and

“friendly”“friendly”►we use numbers between 1 and 1,000we use numbers between 1 and 1,000►minutes or seconds would make some minutes or seconds would make some

common speeds too small (30 mph = common speeds too small (30 mph = 0.5 miles per minute0.5 miles per minute

►days or years would make them too days or years would make them too big (60 mph = 1,440 miles per daybig (60 mph = 1,440 miles per day

4.4. What part(s) of your experiment What part(s) of your experiment design in Part B:design in Part B:

a.a. increased your confidence in your increased your confidence in your results?results?

b.b. decreased your confidence in your decreased your confidence in your results?results?