Answer to Question #12283 in Mechanics | Relativity for aneequa
will the truck have moved before the brakes take hold?
V0 + a * ts = 0
= V0 / (-a)
ts = 21 / 3 = 7 s (the time needed to stop the truck)
distance: S(ts) = V0* ts + a * ts^2 / 2 = 21 * 7 - 3 * 49 / 2
= 147 - 73.5 =
deltaS = D - S(ts) = 110 - 73.5 = 36.5 m
deltaS = V0 *
deltat = deltaS / V0
deltat = 36.5 / 21 = 1.73 s
b) assuming a
reaction of time of 1.4 sec show far behind the car will
the truck stop, and
in how many seconds from the time the driver first
saw the car?
= 1.4 s.
l = D - S(ts) - V0* deltat
l = 110 - 73.5 - 21 * 1.4 = 7.1 m
= deltat + ts
t = 1.4 + 7 = 8.4 s
a) 1.73 s
b) 7.1 m; 8.4
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