Linear Kinematics - Speed Contents: Definition of speed General caveats Speed Example | WhiteboardWhiteboard

Speed –– the rate of motion TOC v avg - average speed (m/s, f/s, mph, km/hr) x,  x- distance (m, cm, feet, miles, km) t,  t - elapsed time (seconds, minutes, hours) Our First Formula! v avg =  x/  t Use math to solve for  x and  t (triangle of mystery) The units must match!

Example: v avg =  x/  t A winch moves a cable 12.5 cm per second. What time will it take to reel in 15 m of cable? First, 12.5 cm/s =.125 m/s, so  x = 15 m v avg =.125 m/s The units match, so now just solve:  t = 15 m/.125 m/s = 120 seconds TOC

Whiteboards: (for no calculators) Speed 11 | 2 | 3 | 4 | TOC For Calculators click here

How fast are you going if you run 27.0 m in 3.0 seconds? v = x/t v = ( 27.0 m) /( 3.0 s) = 9.0 m/s 9.0 m/s W

In what time will a car that is traveling 88.0 f/s go 22 feet? v = x/t 88.0 f/s = (22 f)/t t = (22 f )/(88.0 f/s) =.25 s.25 s W

If you are in a car that is going 30 m/s and you look to the side for 6.0 seconds. How far does the car travel in that time? v = x/t 30 m/s = x/(6.0 s) x = (6.0 s)(30 m/s) = 180 m 180 m W

What time (in days) will it take a glacier that moves 25.0 feet/day to travel 100. yards? 100. yards = 300. feet v = x/t 25.0 f/day = (300 f)/t t = (300 f)/(25.0 f/day) = 12 days 12 days W

What speed must an elevator have if it is to climb 10. floors in 15 seconds? Each story is 3.0 m tall. s = (10. floors)(3.0 m/floor) = 30 m v = x/t v = (30 m)/(15 s) = 2.0 m/s 2.0 m/s W

A winch takes up 12.0 cm of cable a second. What time will it take to reel up 36.0 m of cable? 12.0 cm/s =.120 m/s (make units match) v = x/t.120 m/s = (36.0 m)/t t = 300 s 300. s W

Whiteboards: (Calculators) Speed 11 | 2 | 3 | 4 | TOC

How fast are you going if you run 27.0 m in 3.2 seconds? v avg =  x/  t v avg = 27.0 m / 3.2 s = 8.4 m/s 8.4 m/s W

In what time will a car that is traveling 95.3 f/s go feet? v avg =  x/  t 95.3 f/s = f/  t  t = f /95.3 f/s =.141 s.141 s W

How far will a bullet traveling 350 m/s go in 6.34 seconds? v avg =  x/  t 350 m/s =  x/6.34 s  x = (350 m/s)(6.34 s) = 2200 m 2200 m W

What time (in days) will it take a glacier that moves 15.6 feet/day to travel 100 yards? 100 yards = 300 feet v avg =  x/  t 15.6 f/day = 300 f/  t  t = 300 f/15.6 f/day = 19.2 days 19.2 days W

A car traveling 80. km/hr will go how far (in meters) in 2.7 seconds? 1000 m = 1 km 3600 s = 1 hour (60x60) 80. km/hr(1000m/km) = 80,000 m/h 80,000 m/h/(3600s/h) = m/s v avg =  x/  t m/s =  x/ 2.7 s  x = ( m/s)(2.7 s) = 60 m 60 m W