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Write these down while you wait:1 hr = 60 min = 3600 sec1 km = 1000 m .6214 mile1 mile = 5280 ft = 1760 yards 1609 m1 m 3.281 ft1 yard = 3 feetShortcuts: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 sec1 km = 1000 m .6214 mile1 mile = 5280 ft = 1760 yards 1609 m1 m 3.281 ft1 yard = 3 feetShortcuts: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) = 44 ft/s( hr )( 1 mi )(3600 s)
Dimensional Analysis Contents:•Handy things to know•Ways to convert•Whiteboard practice
Ways to convert units:1. Unit cancellation2. Calculator’s built in (TI 85/86)3. Conversion factors4. Google
Unit cancellation: 30. mph to ft/s:
30. mi(5280 ft)( 1 hr ) hr ( 1 mi )(3600 s) = 44 f/s (note the units canceling)
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 to 466453?)
Calculator (TI 85/86)2nd CONV, MORE, MORE, SPEED, 30 mi/hr > ft/s
Whiteboards: Conversions1 | 2 | 3 | 4 | 5
TOC
Convert 32 mile/hour to feet/second5280 ft = 1 mi3600 s = 1 hr
32 mi(5280 ft)( 1 hr ) = 46.933333 hr ( 1 mi )(3600 s)
47 f/s (2 sig figs)
47 f/s W
Convert 88.0 feet/second to mph5280 ft = 1 mi3600 s = 1 hr
88 ft( 1 mi )(3600 s) = 60 mph s (5280 ft)( 1 hr )
60.0 mph
60.0 mph W
Convert 27.2 m/s to km/hr1000 m = 1 km3600 s = 1 hr
27.2 m ( 1 km )(3600 s) = 97.92 km/hr s (1000 m)( 1 hr )
97.9 km/hr
97.9 km/hr W
Convert 110. km/hr to m/s1000 m = 1 km3600 s = 1 hr
110 km (1000 m)( 1 hr ) = 30.55556 m/s hr ( 1 km )(3600 s)
30.6 m/s
30.6 m/s W
Convert 110. km/hr to mph1 km .6214 mile3600 s = 1 hr ??
110 km (.6214 mi) = 68.354 mph hr ( 1 km )
68.4 mph
68.4 mph W
A car traveling 80. km/hr will go how far (in meters) in 2.7 seconds?1000 m = 1 km3600 s = 1 hour (60x60)(km/hr)/(3.6) = m/s
80. km/hr(1000m/km)(3600s/h) = 22.22 m/s v = x/t22.22 m/s = x/(2.7 s)x = (22.22 m/s)(2.7 s) = 60 m= 60. m
60. m W
A car goes 132 feet in 3.1 seconds. What is its speed in miles per hour?
v = x/tv = (132 f)/(3.1 s) = 42.5806 f/s42.5806 f/s(3600 s/h)/(5280 f/mi) = 29 mph
170 f W
A Baseball going 75 mph takes how much time to go 90. feet?1 mile = 5280 feet3600 s = 1 hour (60x60)1 mph = 1.47 f/s (1.466666... f/s)
75 mi/hr(5280 ft/1 mi)(1 hr/3600 s) = 110 f/sv = x/t110 f/s = (90. f)/tt = (90. f)/(110 f/s) = .818181818 s = .82 s
.82 s W