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20 14 Changchun sanmao mathematics
(1) When the car travels from O to the sign post B:

LOA+△L = v 0△t+v 0(t B-△t)- 12a(t B-△t)2

On the way from O to C:

LOA+2△L = v 0△t+v 0(tC-△t)- 12a(tC-△t)2

Simultaneous equation:

v0= 16m/s

a=2m/s2

(2) The distance from the start to the stop of the car:

x=v0△t+v022a

Available x=72m

Therefore, when the car stops moving, the front end face of the car leaves D between CDs.

LOA+3△L-s-x=44+36-2-72=6m。

Answer: (1) The speed before braking is 16m/s,

The acceleration a after braking is 2m/S2;

(2) When the car stops moving, the distance between the front of the car and D is 6m.