What is acceleration?

What does the term 'negative acceleration' mean?
is it deceleration in the positive direction or is it acceleration in the negative direction?

Reply 1

cookies2312

Acceleration in the negative direction.
Negative acceleration and Deceleration are the same thing
EDIT: I'm sorry, i was thinking of something else.
Deceleration is a reduce in speed/time
Negative acceleration is Acceleration in the opposite direction.

(edited 7 years ago)

Reply 2

IDontKnowReally

Original post by cookies2312

Acceleration in the negative direction.
Negative acceleration and Deceleration are the same thing

But say if car is travelling and then it slows down and eventually stops, it is decelerating but how it is accelerating in the negative direction at the same time?

Reply 3

Alexion

Positive acceleration:

----------------->>

Negative acceleration:

<<-----------------

They're considered positive and negative as they're usually measured along the x-axis - so x increasing (+ve, to the right) or decreasing (-ve, left). In future you may learn about vector direction but I wouldn't worry about that now.

Deceleration is just a term that describes a decrease in speed. So it can be positive or negative acceleration, depending on the direction of motion of the object.

Reply 4

Alexion

Original post by IDontKnowReally

But say if car is travelling and then it slows down and eventually stops, it is decelerating but how it is accelerating in the negative direction at the same time?

Deceleration is a type of acceleration.

It just describes acceleration in the direction opposite to motion - hence the object slows down.

Reply 5

Vikingninja

Original post by IDontKnowReally

But say if car is travelling and then it slows down and eventually stops, it is decelerating but how it is accelerating in the negative direction at the same time?

I would just use negative acceleration. Acceleration is the change in velocity over time so if you are slowing down then you are negatively accelerating.

Reply 6

IDontKnowReally

Original post by Alexion

Deceleration is a type of acceleration.

It just describes acceleration in the direction opposite to motion - hence the object slows down.

So if there is acceleration in one directon, it doesnt necessarily mean the object willl move in that direction?
Would an object have negative acceleration if the accerelation on it was opposite to the direction of motion?

Reply 7

Alexion

Original post by IDontKnowReally

It really depends on the speed of the particle.

Imagine a particle moving forward at 10ms^-1, with an acceleration of -2ms^-2 - this means that the acceleration is acting in the opposite direction to motion. Negative acceleration, if you will.

The particle will decelerate to 0ms^-1 over the course of 5 seconds. But, if it still has the same acceleration, it will begin to speed up in the direction of the acceleration - the opposite direction to the way it was moving before.