An electric vehicle starts from rest and accelerates at a rate of 1.7 m/s^2 in a straight line until it reaches a speed of 22 m/s. The vehicle then slows at a constant rate of 1.5 m/s2 until it stops. (a) How much time elapses from start to stop?

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Answer 1 · 2015-09-07T21:06:50

I found #28s#

Have a look:
enter image source here

Answer 2 · 2015-09-07T21:08:39

#27.56"s"#

For the first leg of the journey:

#v=u+at_1#

#22=0+1.7t_1#

#t_1=22/1.7=12.9"s"#

For the second leg:

#v=u+at_2#

#0=22+(-1.5t_2)#

#t_2=(-22)/(-1.5)=14.66"s"#

Total time #=t_1+t_2=12.9+14.66=27.56"s"#