# Homework Help: Maximum velocity problem

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1. Jan 7, 2017

### Vitalii

1. The problem statement, all variables and given/known data
A train travels a distance of 1,2 km between two stations with an average velocity of 43.2 km/h. During it's motion, at the time t1=40s it moved accelerated, then at time t2 it moved uniformly, then at t3=40s it moved uniformly slowed. Find the maximum velocity of the train.
The acceleration during the slowed motion is equal in modulus to the acceleration during the accelerated motion.

distance=1,2 km
average velocity=43.2 km/h
t1=40s
t3=40s
|a3|= a1

Hopefully it makes sense.

2. Relevant equations

3. The attempt at a solution
I tried solving it by finding the total time. Ttotal=average velocity/total distance. 1.2/43.2=0.027 h or 97.2 seconds

from here i can find t2 which is 97.2-40-40=12.7
after this i'm stuck and don't know what to do next.

2. Jan 7, 2017

### PeroK

You could try drawing a graph of velocity against time.

3. Jan 7, 2017

### Vitalii

How exactly can i draw a graph of velocity against time with all my known data?

4. Jan 7, 2017

### PeroK

What's the problem? It accelerates, it moves at constant speed for a time, then it decelerates to a stop. You can draw that.

5. Jan 7, 2017

### Vitalii

How do i draw a velocity against time graph?

6. Jan 7, 2017

### PeroK

You put time along the x-axis and velocity along the y-axis, then you draw the velocity as a function of time.

You need to know that distance travelled is the area under the velocity-time graph.

Do they not teach you this anymore?