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# negative acceleration/velocity

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1. In mechanics when the acceleration or velocity is negative does that mean it is slowing down or moving backwards?
2. If it has negative velocity, it is moving backwards.
If it has positive velocity and negative acceleration it is decelerating.
If it has negative velocity and negative acceleration it is accelerating.

I think?
3. (Original post by Dusky Mauve)
If it has negative velocity, it is moving backwards.
If it has positive velocity and negative acceleration it is decelerating.
If it has negative velocity and negative acceleration it is accelerating.

I think?
yeah always draw out a diagram and chose a direction to be positive, helps a lot
4. (Original post by Dusky Mauve)
If it has negative velocity, it is moving backwards.
If it has positive velocity and negative acceleration it is decelerating.
If it has negative velocity and negative acceleration it is accelerating.

I think?
Thanks
5. (Original post by TSRPAV)
yeah always draw out a diagram and chose a direction to be positive, helps a lot
Yeah, i draw out diagrams but dont really understand what it means to make up +ve. Ive just learnt it if that makes sense.

E.g. if the acceleration = -9.8 would displacement be +ve and vice versa?

I was doing a question the other day where a = -9.8 and displacement was also -ve which confused me. :/

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