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Does deceleration mean opposite direction to motion?

If the direction of motion was rightwards, and the car was decelerating, does that mean the car must have turned around and is going in the opposite direction.
Original post by dont know it
If the direction of motion was rightwards, and the car was decelerating, does that mean the car must have turned around and is going in the opposite direction.


Deceleration just means the velocity decreases, so for a car going from 5 m/s down to 2 m/s is deceleration, however the car here would still be going forward until velocity hits 0, at which point the car would become stationary. If it begins going backwards, then that means the velocity is -ve, and it keeps getting more -ve (hence it still decreases) and so the car decelerates while going backwards.

So no, decelerating doesnt really mean that it must be going back.
(edited 6 years ago)
Original post by RDKGames
Deceleration just means the acceleration decreases, so for a car going from 5 m/s/s down to 2 m/s/s is deceleration, however the car here would still be going forward until acceleration hits 0, at which point the car would become stationary. If it begins going backwards, then that means the acceleration is -ve, and it keeps getting more -ve (hence it still decreases) and so the car decelerates while going backwards.


I think you mean speed or velocity. Deceleration refers to a reduction in speed. Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed. Let me know if you need any more help understanding this!
Original post by RDKGames
Deceleration just means the acceleration decreases, so for a car going from 5 m/s/s down to 2 m/s/s is deceleration, however the car here would still be going forward until acceleration hits 0, at which point the car would become stationary. If it begins going backwards, then that means the acceleration is -ve, and it keeps getting more -ve (hence it still decreases) and so the car decelerates while going backwards.


I think you're confusing acceleration and velocity there.
Reply 4
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RichE
15
Original post by RDKGames
Deceleration just means the acceleration decreases, so for a car going from 5 m/s/s down to 2 m/s/s is deceleration, however the car here would still be going forward until acceleration hits 0, at which point the car would become stationary. If it begins going backwards, then that means the acceleration is -ve, and it keeps getting more -ve (hence it still decreases) and so the car decelerates while going backwards.


Do you mean until velocity hits zero.

And that velocity is -ve when it's going backwards.

It sounds like acceleration is -ve throughout the scenario above.
Original post by chailatte2407
I think you mean speed or velocity. Deceleration refers to a reduction in speed. Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed. Let me know if you need any more help understanding this!


Yes you're right, got distracted there.
Original post by chailatte2407
I think you mean speed or velocity. Deceleration refers to a reduction in speed. Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed. Let me know if you need any more help understanding this!


Speed is scalar ie magnitude only, velocity is a vector. Deceleration is a vector as it is a change in velocity.

This sentence "Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed." is wrong. If an object is going round a corner at constant speed its velocity is changing so it is accelerating.
I think you might need to check on this ..
Original post by Muttley79
Speed is scalar ie magnitude only, velocity is a vector. Deceleration is a vector as it is a change in velocity.

This sentence "Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed." is wrong. If an object is going round a corner at constant speed its velocity is changing so it is accelerating.
I think you might need to check on this ..


Additional caveats and special cases that are no doubt of no concern to OP who currently thinks that deceleration means turning around and going the opposite way. Let us save such lofty ideas for another time my good man (such that we may discuss them away from the plebs)
Reply 8
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Treesha
7
Think of a car slowing down it’s speed, catching its brakes ...
Reply 9
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RichE
15
Original post by Muttley79

This sentence "Also, if the acceleration of a car is 0, it's not necessarily stationary, it could also be travelling at a constant speed." is wrong.


There's nothing wrong with that statement. He is not claiming that constant speed implies no acceleration, only that no acceleration does not imply a stationary car.
Original post by RichE
There's nothing wrong with that statement. He is not claiming that constant speed implies no acceleration, only that no acceleration does not imply a stationary car.


Mixing speed and acceleration up in a sentence is loaded with problems - I would not advise anyone to express it like this.
Original post by chailatte2407
Additional caveats and special cases that are no doubt of no concern to OP who currently thinks that deceleration means turning around and going the opposite way. Let us save such lofty ideas for another time my good man (such that we may discuss them away from the plebs)


I am not male ...
Original post by Muttley79
I am not male ...


Hahahaha that's a good one
Original post by chailatte2407
Hahahaha that's a good one


What? Explain ...
Reply 14
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RichE
15
Original post by Muttley79
Mixing speed and acceleration up in a sentence is loaded with problems - I would not advise anyone to express it like this.


How was the poster's comment anything except correct? Zero acceleration does not imply zero speed or velocity, which addressed a confusion of the OP. Your post was/is wrong and liable to confuse the OP if anything was.
Going back to the OP

If unbalanced Force (and therefore acceleration) is in the oppositte direction to motion, then YES it will produce a deceleration. The object will decelerate until its velocity is zero and THEN it will begin to accelerate again in the opposite direction (assuming the unbalanced force is still acting).
Original post by RichE
How was the poster's comment anything except correct? Zero acceleration does not imply zero speed or velocity, which addressed a confusion of the OP. Your post was/is wrong and liable to confuse the OP if anything was.


No I disagree, the OP is confused about scalars and vectors so the statement would just confuse them more when they meet circular motion. Many studnets get confused with a similar statement and can't see that something changing direction but not speed is changing velocity and is therefore accelerating.
Reply 17
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RichE
15
Original post by Muttley79
No I disagree, the OP is confused about scalars and vectors so the statement would just confuse them more when they meet circular motion. Many studnets get confused with a similar statement and can't see that something changing direction but not speed is changing velocity and is therefore accelerating.


None of that changes the fact that you have made factually incorrect claims on this thread which you're still to correct.

And there is very little in the original post to suggest any confusion between scalar and vector quantities. The entire question is posed within a single parameter scenario and the confusion is obviously between an idea of negative acceleration and negative velocity.

In any case what you claimed was wrong was not wrong - if you thought it could be better explained fine, but that didn't make it wrong.

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