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An electric vehicle starts from rest and accelerates at a rate of 2.0 m/s2 in a straight line until it reaches a speed of 20 m/s. The vehicle then slows at a constant rate of 1.0 m/s2 until it stops.

(a) How much time elapses from start to stop?
(b) How far does the vehicle travel from start to stop?

Respuesta :

HomertheGenius
a) 1st phase:
v= a*t,   t=v/a=[tex] \frac{20 m/s}{2m/s^{2} } [/tex]=10s
2nd phase:
0 m/s= 20 m/s - a*t,  a*t= 20 m/s, t=[tex] \frac{20 m/s}{1m/s^{2} } [/tex]=20s
Total time: t1+t2=10 s+20 s = 30 s
b)Formula:  s=v0*t+at²/2 or s=v0*t-at²/2
1st phase:
s=0+[tex] \frac{2*10^{2} }{2} [/tex]=100m
2nd phase:
s=20 m/s*20 s-[tex] \frac{1*20^{2} }{2} [/tex]=200 m
Total distance traveled: s1+s2 = 100 m + 200 m = 300 m.
  

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