Answer to Question #169378 in Mechanical Engineering for Macdonald

Question #169378

An electric train start from a station and maintained an acceleration of 0.9m/s2 for 20 seconds, if it then travel for 80 seconds with uniform velocity and finally has a uniform retardation which brings it to rest in a further 10 seconds. calculate the retardation and the total distance covered.


1
Expert's answer
2021-03-08T03:09:04-0500

Speed after 20 seconds:


v=atv=at

Distance covered in 20 s:


d=vt/2d=vt/2

Distance covered in 80 seconds of uniform motion:


x=vT=atTx=vT=atT

Retardation:


ar=v/τ=at/τ=1.8 m/s2.a_r=v/\tau=at/\tau=1.8\text{ m/s}^2.

Distance in retardation:


r=vτ/2=atτ/2r=v\tau/2=at\tau/2

Total distance:


X=d+x+r==at(0.5+T+0.5τ)==0.920(0.5+80+0.510)=1539 m.X=d+x+r=\\ =at(0.5+T+0.5\tau)=\\ =0.9·20(0.5+80+0.5·10)=1539\text{ m}.


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Comments

Assignment Expert
09.03.21, 14:20

Dear Macdonald, You're welcome. We are glad to be helpful. If you liked our service please press like-button beside answer field. Thank you!

Macdonald
08.03.21, 10:11

Thank you so much its correct

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