In an emergency,a car moving at 50km/h cna be stopped in 15m. What is the stopped distance of the car if the speed is 70km/h,assume the same deceleration?
A.7.7m
B.10.9m
C.17.7m
D.21.0m
E.29.4m
唔該列埋算式
position and movement
2009-10-12 5:27 am
回答 (1)
2009-10-12 5:53 am
✔ 最佳答案
Initial velocity, u = 50 km/h = 50 / 3.6 = 13.89 m/sFinal velocity, v = 0
Stopping distance, s = 15 m
By equation of motion,
v2 = u2 - 2as
0 = (13.89)2 - 2a(15)
Deceleration, a = 6.43 ms-2
Now, initial velocity, u = 70 km/h = 70/3.6 = 19.44 m/s
By equation of motion,
v2 = u2 - 2as
0 = (19.44)2 - 2(6.43)s
Stopping distance, s = 29.4 m
The answer is E.
參考: Physics king
收錄日期: 2021-04-19 15:30:26
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091011000051KK02085