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速度.加速度的問題

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the redcar and green car, identical expect for the color,move toward each other in adjacent lanes and parallel to an x axis. At time=0, the red car is at xr=0 and the green car is at xg=220m If the red car has a constant velocity of 20 km/h ,the car pass each other at x=44.5m ,and if has a constant velocity of... 顯示更多 the redcar and green car, identical expect for the color,move toward each other in adjacent lanes and parallel to an x axis. At time=0, the red car is at xr=0 and the green car is at xg=220m If the red car has a constant velocity of 20 km/h ,the car pass each other at x=44.5m ,and if has a constant velocity of 40km/h , they pass each other at x=76.6m. What are (a) the inital velocity and (b) he acceleration of the green car? 請問這提該怎麼算呢!? 希望可以加上完整的文字說明!!謝謝

最佳解答:

這題有兩個未知數:綠車加速度和會車時間,需要兩個公式來解.這兩個公式可以用紅車速度和會車距離來聯立.1. 會車時綠車走了220-44.5=Vt+at2/2, 而t=44.5/(20*1000/3600)=8.01,故 175.5=8.01V+32.08a [1].2. 同理,t=76.6/(40*1000/3600)=6.894, 143.4=6.894V+23.764a [2],解得(a)V=((175.5*23.764-143.4*32.08)/{8.01*23.76-6.894*32.08)=13.95 m/s, (b)a=2.684 m/s2.

其他解答:

剛剛驗算了一下!發現妳的加速度a有計算錯誤>"<