1) A sports car accelerates along a straight line from rest at a rest of 6ms^-2 for 4s and then its acceleration changes to -4ms^-2 for 2s.
(a) Find the maximum speed of the car. Express the answer in km h^-1.
(b) Find the final speed of the car. Express the answer in km h^-1.
(c) Find the average acceleration of the car. Express the answer in m s^-1.
10分About Physics要交功課.唔該幫幫手
2007-10-16 2:46 am
回答 (1)
2007-10-16 2:59 am
✔ 最佳答案
1.a. By v = u + at v = 0 + (6)(4)
Maximum speed, v
= 24 ms-1
= 24 X 3600 / 1000
= 86.4 kmh-1
b. By v’ = v + a’t’
v’ = 24 + (-4)(2)
Final speed, v’
= 16 ms-1
= 16 X 3600 / 1000
= 57.6 kmh-1
c. Change of speed
= 16 – 0
= 16 ms-1
Total time
= 4 + 2
= 6 s
So, average acceleration
= change of speed / time
= 16 / 6
= 2.67 ms-2
參考: Myself~~~
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