Читать книгу Physics I For Dummies - Steven Holzner - Страница 54

Average speed differs from instantaneous speed, unless you’re traveling in uniform motion (in which case your speed never varies). In fact, because average speed is the total distance divided by the total time, it may be very different from your instantaneous speed.

If you travel 2,781 miles in 4.000 days (a total of 96 hours), you go at an average speed of 28.97 miles per hour. That answer seems pretty slow, because when you’re driving, you’re used to going 65 miles per hour. You’ve calculated an average speed over the whole trip, obtained by dividing the total distance by the total trip time, which includes non-driving time. You may have stopped at a hotel several nights, and while you slept, your instantaneous speed was 0 miles per hour; yet even at that moment, your overall average speed was still 28.97 miles per hour!