Just how fast do you think you were going, Sir? Speed Just how fast do you think you were going, Sir?

Definition Speed is how slow or fast you are changing position. We usually measure speed in the US in miles per hour (mph) or in science in meters per second (m/s)

Italian physicist Galileo Galilei (1564 – 1642) is credited with being the first to measure speed by considering the distance covered and the time it takes. Galileo defined speed as the distance covered per unit of time.

Speed Formula S(m/s) T(s) Speed is distance divided by time S = D/T or D (m) S(m/s) T(s)

PROBLEMS As in math, please SHOW the SETUP and your WORK. A man walks 3 miles in 45 min. How fast is he walking? If one variable is on the top, & the other on the bottom, divide. S = ? 3m D = 3 miles T = 45 min S = ? T = 45 min

Or we multiply our answer by 60 (min/hr) & could say 3.6 m/hr 3 miles = .06 m/min 45 minutes Or we multiply our answer by 60 (min/hr) & could say 3.6 m/hr

One more! How long does it take to go from Green Bay to Chicago (207 miles or 333 km) if my average speed is 45 miles an hour? 207 mi 207mi ÷ 45mi/hr = 4.6 hrs 45 m/h ?

Last one! How far has Sally driven if she travels 3 hrs at 15 k/hr? If both variables are on the bottom, multiply. ? 15 k/hr X 3 hr = 45 k 15k/h 3 hr

NOTE! Setup is shown (either circle or formula) Answer has label 1 sec = 1/60 of a minute = 1/3600 of an hour 1 min = 1/60 of an hour

PUBLIC SERVICE ANNOUNCEMENT Speed is a factor in 30% of fatal accidents At 25 mph, the chance of being killed is 1 in 31.  At 55 mph, the chance of being killed is 1 in 16. At 75 mph, the chance of being killed is 1 in 2. Drive safely; don’t speed.