一、已知物体运动的各段路程和对应时间，求平均速度．如图1所示．例1某同学赛跑时，头2秒内跑了12米．接着又用6秒时间跑了4O．8米．最后用1秒时间跑了72米，求全程中的平均速度．解S一出十sZ＋S。一12米十40．8米十7．2米一60米t—ti＋t。牛t3—2秒W6秒WI秒一9秒S60Xi＿＿， First, each section of the known object movement and the corresponding time, seeking the average speed. As shown in Figure 1. Example 1 When a classmate raced, he ran 12 meters in the first 2 seconds. Then he ran for 4 seconds in 6 seconds. 8 meters. In the end, I ran 72 meters in 1 second to find the average speed in the whole process. Solve a ten sZ+S. A 12m to a 40.8m to a 7.2m to a 60m t-ti+t. Cow t3-2 seconds W6 seconds WI seconds 9 seconds S60Xi__