form 4 physicis
2007-09-26 7:04 pm
A car is travelling at 70km/h. the driver then sees a 50 km/h speed limit sigh at a distance of 30m ahead. In order not to exceed the speed limit, find the minimun deceleration of the car.
回答 (2)
2007-09-26 7:10 pm
✔ 最佳答案
Initial speed, u = 70 kmh-1 = 70 kmh-1 X (1000 m / 1 km) X (1 h / 3600 s) = 19.44 ms-1 Final speed, v = 50 kmh-1 = 50 kmh-1 X (1000 m / 1 km) X (1 h / 3600 s) = 13.89 ms-1
Displacement, s = 30 m
By v2 = u2 + 2as
(13.89)2 = (19.44)2 + 2a(30)
a = -3.08 ms-2
So, the minimum deceleration of the car is 3.08 ms-2.
參考: Myself~~~
2007-09-26 7:11 pm
-3.09ms^-2
收錄日期: 2021-04-13 18:43:58
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070926000051KK01114