※ 引述《MICKAAELan (米K)》之銘言:
: 想請教大大一題物理,
: 因為看不懂題意,卡關好久,GOOGLE大神也只幫忙找到付費網站的解答@@
: 拜託各位大大了!
: 題目如下:
: A car is 200 m from a stop sign and traveling toward the sign at 40.0 m/s.
: At this time, the driver suddenly realizes that she must stop the car.
: If it takes 0.200 s for the driver to apply the brakes,
: what must be the magnitude of the constant acceleration of the car after
: the brakes are applied so that the car will come to rest at the stop sign?
: 只能選擇一個:
: a. 2.08 m/s^2
: b. 4.17 m/s^2
: c. 3.42 m/s^2
: d. 3.89 m/s^2
: e. 2.89 m/s^2
在踩下剎車所花費的0.2秒時間 車子又行進了40*0.2=8(公尺)
又200-8=192(公尺)
因此在離停止標誌尚192公尺之後開始進行等加速度運動
由此帶入v^2=v0^2+2ax之公式
得到0^2=40^2-2*a*192
求得a=4.17 (近似值)
有錯誤請各位前輩指教改正