In a 400M race, a runner first accelerates uniformly from rest to a speed of 8ms-1. He then maintains this speed and finishes the race in 52s. How long does the rinner take to reach the speen of 8ms-1.
豬脾
2007-10-16 22:03
let t=xs
4x((u+v)t/2)+8(52-x)=400 16=4x x=4s
豬脾
2007-10-16 22:06
引用第1樓卡卡....於2007-10-16 22:03發表的“”: let t=xs 4x((u+v)t/2)+8(52-x)=400 16=4x x=4s
仲有一個: consider v-t graph
area under the curve咪好似個梯形 又係let t=xs
((52-x)+52)8/2=400
dinlo
2007-10-16 22:09
引用第1樓卡卡....於2007-10-16 22:03發表的“”: let t=xs 4x((u+v)t/2)+8(52-x)=400 16=4x x=4s