# Homework Help: Acceleration of a Train Problem

1. Sep 16, 2008

### Husker70

1. The problem statement, all variables and given/known data
A train slows down as it rounds a sharp horizontal turn, slowing from
90.0 km/h to 50.0km/h in that 15.0s that it takes to round the bend. The
radius of the curve is 150m. Compute the acceleration at the moment the train
speed reaches 50.0 km/h. Assume that it continues to slow down at this time at
the same rate.

2. Relevant equations

3. The attempt at a solution
Find the radial and tangential accelerations then get total acceleration. Direction
will be tan-1 of those. I've tried to start but my numbers don't seem to be
right. I've drawn a sketch.
Thanks,
Kevin
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 17, 2008

### ritwik06

Please do post what you have calculated. What you say seems perfectly right to me.

3. Sep 17, 2008

### Husker70

First I find the velocity by taking 50.0km/h - 90.0 km/h / 15s
I converted the km to 833.3m/s - 1500m/s/15s
I get velocity to be -44.4m/s
I used the radial acceleration equation (-44.4m/s)2 / 150m to get 13.14m/s2 inward.
I'm not sure how to get the tangential from here.
Thanks,
Kevin

4. Sep 17, 2008

### ritwik06

You made an error converting from Km/h to m/s
90 Km/hr= 25 m/s
50 Km/hr=13.8889 m/s

a(tangential)=(25-13.8889)/15
a(radial)= $$v^{2}/r$$ where v=13.8889 an r=150

5. Sep 17, 2008

### Husker70

I'm not sure where my conversion came from
I get a tan acc to be .74 m/s2
I get a radial acc to be 1.2860 m/s2

I get 1.48 m/s2 inward acceleration by squaring the acceleration and then
getting the square root.

For angle is the tan/radial or is the radial/tan to figure angle?

Thanks for your help. I'm understanding this alot better.

Kevin