How exactly does a dynamicist define deceleration in this case?

[gikiian]

Hey friends. I wanted to know how exactly would a dynamicist define deceleration of a car on a road with humps and dips. Actually I always thought that deceleration of car on the road will be the vector a (see the diagram), however, in a sample problem in my dynamics book, it the car's deceleration is taken as the vector a_t (see the diagram), but it is not explicitly mentioned to be the tangential component. So how do we differentiate between the two cases?

 

[OldEngr63]

First off, dynamicists usually speak in terms of acceleration, rather than deceleration.

You question seems to revolve around whether the term refers to the tangential component or the total vector. Unless otherwise specified, I would usually assume that the total vector is implied, but anytime there seems to be confusion, the only option is to ask for clarification.

 

[gikiian]

I believe what you're saying is correct. Thanks!