Write these down while you wait:
1 hr = 60 min = 3600 sec
1 km = 1000 m  .6214 mile
1 mile = 5280 ft = 1760 yards  1609 m
1 m  3.281 ft
1 yard = 3 feet
Shortcuts:
1 m/s = 3.6 km/hr  2.237 mph, (mph = miles/hour)
1 mph  1.47 f/s (1.46666666…)
1 f/s  .682 mph (.6818181818…)
Answer This Question:
How many feet per second is 30 mph? (use any method
you want – including help from others – but have an
answer)
Write these down while you wait:
1 hr = 60 min = 3600 sec
1 km = 1000 m  .6214 mile
1 mile = 5280 ft = 1760 yards  1609 m
1 m  3.281 ft
1 yard = 3 feet
Shortcuts:
1 m/s = 3.6 km/hr  2.237 mph,
(mph = miles/hour)
1 mph  1.47 f/s (1.46666666…)
1 f/s  .682 mph (.6818181818…)
Answer This Question:
How many feet per second is 30 mph? (use any method you want – including help from
others – but have an answer)
(30 mph)(1.4666666) = 44 ft/s
(30 mi)(5280 ft)(1 hr)
( hr )( 1 mi )(3600 s)
= 44 ft/s
Dimensional Analysis Contents:
•Handy things to know
•Ways to convert
•Whiteboard practice
Ways to convert units:
Unit cancellation:
30. mph to ft/s:
1.
2.
3.
4.
Unit cancellation
Calculator’s built in (TI 85/86)
Conversion factors
Google
30. mi(5280 ft)( 1 hr )
hr ( 1 mi )(3600 s) = 44 f/s (note the units canceling)
Calculator (TI 85/86)
2nd CONV, MORE, MORE, SPEED, 30 mi/hr > ft/s
Conversion factor:
30. mph to ft/s: (1 mph = 1.47 f/s)
30. mph x (1.47) = 44.1 = 44 ft/s
(slightly off - what’s the “real” conversion factor?)
Google:
Type 30. mph in ft/s into the search bar (text it?)
TOC
Whiteboards:
Conversions
1|2|3|4|5
TOC
Convert 32 mile/hour to feet/second
5280 ft = 1 mi
3600 s = 1 hr
32 mi(5280 ft)( 1 hr ) = 46.933333
hr ( 1 mi )(3600 s)
47 f/s (2 sig figs)
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
47 f/s
W
Convert 88.0 feet/second to mph
5280 ft = 1 mi
3600 s = 1 hr
88 ft( 1 mi )(3600 s) = 60 mph
s (5280 ft)( 1 hr )
60.0 mph
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
60.0 mph
W
Convert 27.2 m/s to km/hr
1000 m = 1 km
3600 s = 1 hr
27.2 m ( 1 km )(3600 s) = 97.92 km/hr
s (1000 m)( 1 hr )
97.9 km/hr
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
97.9 km/hr
W
Convert 110. km/hr to m/s
1000 m = 1 km
3600 s = 1 hr
110 km (1000 m)( 1 hr ) = 30.55556 m/s
hr ( 1 km )(3600 s)
30.6 m/s
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
30.6 m/s
W
A Baseball going 75 mph takes how
much time to go 90. feet?
(hint convert mph to ft/s first)
75 mi/hr(5280 ft/1 mi)(1 hr/3600 s) =
110 f/s
v = s/t
110 f/s = (90. f)/t
t = (90. f)/(110 f/s) = .818181818 s = .82 s
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
.82 s
W
A car traveling 80. km/hr will go how
far (in meters) in 2.7 seconds?
(hint convert km/hr to m/s first)
80. km/hr(1000m/km)(3600s/h) = 22.22 m/s
v = s/t
22.22 m/s = x/(2.7 s)
s = (22.22 m/s)(2.7 s) = 60 m= 60. m
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
60. m
W
A car goes 132 feet in 3.1 seconds.
What is its speed in miles per
hour?
(find the answer, and convert to mph)
v = s/t
v = (132 f)/(3.1 s) = 42.5806 f/s
42.5806 f/s(3600 s/h)/(5280 f/mi) = 29 mph
Shortcuts: (mph = miles/hour)
1 m/s = 3.6 km/hr  2.237 mph  3.281 ft/s
1 mph  1.467 f/s (1.46666666…)  1.609 km/hr  0.4470 m/s
1 f/s = 0.3048 m/s  .6818 mph (.6818181818…)  1.0973
km/hr
1 km/hr  0.2778 m/s  0.6214 mph  0.9113 ft/s
170 f
W