a car moves along a straight road.it slows down uniformly at a rate of 4ms^-2 for 4.75s and stops in front of a traffic light.after waiting for 2 mins ,the traffic light turns green and the car accelerates uniformly at 3ms^-2 to 17 m/s .
a)1)what is the initial veloctiy of the car?
2)hence,what is the displacement of the car before it stops in front of the traffic light?
b)what is the displacement of the car between starting from rest and moving at 17m/s?
physis
2007-10-15 1:33 am
回答 (1)
2007-10-15 2:09 am
✔ 最佳答案
(a) 1) u = ? ms^-1 v = 0ms^-1 a = 4ms^-2 t = 4.75sApplying v = u+ at
0 = u + (-4)(4.75)
u = 19 ms^-1
(a) 2) u = 19 ms^-1 v = 0ms^-1 a = 4ms^-2 s = ? m
Applying v^2 - u^2 = 2as
0^2 - 19^2 = 2(-4)s
-361/-8 = s
s = 45.125m
b) u = 0 ms-1 v = 17 ms-1 a = 3ms^-2 s = ?m
Applying v^2 - u^2 = 2as
17^2 - 0^2 = 2(3)s
289/6 = s
s = 48.16666667
= 48.7 m
Hope this help
參考: Me
收錄日期: 2021-04-13 13:55:29
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