Physics - Intro 03

Sig Figs and Railroad Tracks Continue

OPENING QUESTION: Take about 5 minutes to write down 5 (or so) numeric values (including scientific notation!). Quiz the other folks at your table (and have them quiz you) on Sig Figs.

OBJECTIVES:

I will be able to successfully identify significant figures for MOST values I observe today.

I will be able to setup basic railroad track conversions during class today

 

WORDS O' THE DAY:

  • Sig Figs

WORK O' THE DAY:

════════════════════════

1) The circumferance of the Earth is about 25,000 miles around.

  • Please convert that value into millimeters using railroad tracks
  • Now please write your answer in scientific notation

2) Usain Bolt ran the 100. meters at the 2009 World Track & Field Championships with a time of 9.58 seconds-- a world record that still stands.

  • Convert that distance into miles using railroad tracks
  • Convert that time into hours using railroad tracks
  • What was Usain Bolt's speed (in miles per hour? HINT: DO NOT USE RR Tracks for this one)
  • Is it possible to do both of the above steps at once, using RR Tracks?

3) Irma was one of the strongest hurricanes ever recorded when it hit the easter Caribbean last fall where maximum wind gusts were meaured at 221.50 mph. Please convert that windspeed to meters/sec:

4) How many meters in a kilometer?

5) How many millimeters in a centimeter?

6) How many centimeters in meter?

7) How many centimeters in a kilometer?

 

ANSWER:

Here's a step-by-step on converting 221.50 mph into meters/sec

Let's do the linear measure first:

1) miles go to feet

221.50 miles
feet
 
1 hr
miles
 

2) feet go to inches

221.50 miles
feet
in
         
1 hr
miles
feet
         

3) inches go to centimeters (this is where we cross-over to metric)

221.50 miles
feet
in
cm
       
1 hr
miles
feet
in
       

4) centimeters go to meters

221.50 miles
feet
in
cm
m
     
1 hr
miles
feet
in
cm
     

5) now fill in the relationship in each column as follows:

221.50 miles
5280 feet
12 in
2.54 cm
1m
   
1 hr
1 miles
1 ft
1 in
100 cm    

Now let's finish the tracks but turning hours into seconds

6) let's do the time part all at once:

221.50 miles
5280 feet
12 in
2.54 cm
1m
1 hr
1 min
1 hr
1 miles
1 ft
1 in
100 cm
60 min
60 sec

7) Let's now check our units and make sure everything cancels appropriately:

221.50 miles
5280 feet
12 in
2.54 cm
1m
1 hr
1 min
1 hr
1 miles
1 ft
1 in
100 cm
60 min
60 sec

 

 

HOMEWORK: