How Long and Fast Does a Diesel Train Accelerate to Cover 6km?

[scotthands]

Homework Statement

A deisel train accelerates uniformly from rest to reach 60km/hr in 6 minutes, after which the speed remains constant.
Calculate the total time taken to travel 6km and the acceleration.

Homework Equations

s= ut
v= u+at
s=ut + 0.5*at^2

The Attempt at a Solution

I'm not sure how to incorporate the accelaration part into the question.
I tried t=(v-u)/a but idon't know what to put in for the acceleration.

 

[qspeechc]

That is not a question.

 

[scotthands]

yeah i accidentally entered the post before i finished it, it's finished now.

 

[qspeechc]

Well the time taken to accelerate is 6min, because we are given that.

First find the distance traveled in the 6mins it is accelerating.

6mins = 1/10 hours. We must find the acceleration.

Re-arrange v= u+at for acceleration:

a = (v - u)/t = 60/(1/10) = 600 km/h^2

Now find the distance it travels:

s=ut + 0.5*at^2 = 0 + 0.5*600*(1/10)^2 = 3km

Therefore the train still has 3km left to go, but now it is traveling at a constant 60km/h, so the time taken is:

s = ut
so:
t = s/u = 3/60 = 1/20 of an hour = 3mins

So the total time for the journey is 9mins

 

[scotthands]

thank you

 

[qspeechc]

My Pleasure.