A car is accelerating linearly from 10ms^-1 with a uniform acceleration 5ms^-2
a)find the velocity of the car after 5s
b)find the total displacement of the car after 5s
c)the driver applies brake after accelerating for 5s,if the braking distance is 30m,find the deceleration of the car.
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Mechanics.....
2006-12-03 9:11 am
回答 (1)
2006-12-03 9:19 am
✔ 最佳答案
a) v = u + at= 10 + 5*5
= 35 m/s
So the velocity of the car after 5s is 35m/s.
b) s = ut + 1/2*at^2
= 10(5) + 0.5*5*5^2
= 112.5 m
So the total displacement of the car is 112.5m.
c) v^2 - u^2 = 2as (Now v = 0, u = 35 from (a))
0 - 35^2 = 2*a*30
a = -20.4m/s^2 (negative means deceleration)
So the deleration of the car made by the braking action is 20.4m/s^2
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