1)A car of mass 1500 kg travels at 108 km h-1.It is braked to stop with a braking force of 6000N.
a)How long does it take to stop the car?
b)What is the braking distance?
Phy 求救 F4 mechanics
2008-02-24 10:05 pm
回答 (1)
2008-02-24 10:24 pm
✔ 最佳答案
(change v into SI unit first)
v = 108(1000/3600)=30 ms-1
F = ma
6000 = 1500 a
a = 4 ms-2
v = u+at
0 = 30+(-4)t (negative because a and v are in opposite direction)
t = 7.5s
b)
by v2-u2 = 2as
302 – 0= 2(4)(s)
s = 112.5m
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