# Homework Help: Train Turning

1. Jun 12, 2009

### blackboy

1. The problem statement, all variables and given/known data
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
Kinematics
Circular Motion

3. The attempt at a solution
I understand we have to add the tangential acceleration to the centripetal acceleration. Can I just treat this motion as a straight line to compute the tangential acceleration? Can we do this for most problems like this? If so, then the tangential acceleration is -2.67 m/s^2. Then the total acceleration is 2.96 m/s^2 64.28 degrees of the radius.

2. Jun 12, 2009

### rock.freak667

I assumed you used "90.0 km/h to 50.0km/h in that 15.0s" to get the tangential acceleration of -2.67m/s2?

and then used 50km/h in 150m radius for the normal acceleration right?

then added them up using a vector method?

If so then it should be correct.

3. Jun 12, 2009

### blackboy

Yes, but can we pretend it was 1-d kinematics to find the tangential acceleration?

4. Jun 12, 2009

### rock.freak667

that is how you found the tangential acceleration, so yes.