Homework Help: Train turning, tangential acceleration and total acceleration

1. Sep 17, 2010

gap0063

1. (a)A train slows down at a constant rate as it
rounds a sharp circular horizontal turn. Its
initial speed is not known. It takes 16.6 s to
slow down from 86 km/h to 30 km/h. The
radius of the curve is 162 m.
As the train goes around the turn, what is
the magnitude of the tangential component of
the acceleration?

(b) As the train goes around the turn, what is
the sign of the tangential component of the
acceleration? Take the direction in which the
train is moving to be the positive direction.
1. +
2. Not enough information
3. 0
4. −

(c)At the moment the train’s speed is 50 km/h,
what is the magnitude of the total accelera-
tion?

2. Relevant equations
atangential = d|v|/dt
not sure on others

3. The attempt at a solution
I tried part (a) with atangential = d|v|/dt
where atangential = |30-86|/16.6=3.37349 km/h^2
then converting to m/s^s by times 3600s and dividing 1000m and getting 12.1446 m/s^2
wrong

2. Sep 17, 2010

PhanthomJay

You are messing up your units and conversions....first change km/hr to m/s, find the change in v, then divide by t (in seconds) to get the tangential acceleration.