# accelerate vs speed up

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#### Normandete

##### Senior Member
Is there any difference between speed up and accelerate?

Thank you

• #### lgs

##### Senior Member
No, but speed up as a term is less formal than accelerate.

#### Egmont

##### Senior Member
If you mention a numerical rate at which speed is increasing, use accelerate: "Falling objects accelerate at 32.2 feet per second squared in earth's gravity."

In a general discussion, such as describing what a car did after leaving heavy traffic for the open road, either one works.

#### George French

##### Senior Member
Is there any difference between speed up and accelerate?

Thank you
Yes and no... If you are in the middle of a physics lesson then there is. In normal descriptions used by the man in the street there is no difference.

GF..

If you are interested then take a look at this Wikipedia page http://en.wikipedia.org/wiki/Acceleration

#### Parentheses

##### New Member
"Accelerate" in scientific contexts also includes slowing down, which is negative acceleration.

Most of us would call this "deceleration", but when you are counting numbers and trying to maintain consistency, it is more useful to think in terms of positive and negative acceleration.

Hope that makes sense.

#### Normandete

##### Senior Member
What I have understood is that accelerating and speeding up a car is the same concept for a man in the street. However if we enter a scientific context acceleration can be negative or positive depending of the vector's direction and its module value.

Is that right?

Thank you all!

#### Parentheses

##### New Member
You are right.

For the man in the street, "accelerating" and "speeding up" are exactly the same.

For the physicists or other pedants considering vectors, they are not.

#### Thomas Tompion

##### Senior Member
Is there any difference between speed up and accelerate?

Thank you
Give us some contexts, Normandete. The two aren't interchangeable in many circumstances.

#### Xavier da Silva

##### Senior Member
Give us some contexts, Normandete. The two aren't interchangeable in many circumstances.
Contexts:

John, speed up the car or we won't arrive in time for the meeting. Vs John, accelerate the car or we won't arrive in time for the meeting.

What is the difference in this case?

Thank you in advance!

#### DonnyB

##### Sixties Mod
John, speed up the car or we won't arrive in time for the meeting. Vs John, accelerate the car or we won't arrive in time for the meeting.

What is the difference in this case?
They both sound very odd, and I don't think you can use "accelerate" transitively like that.

Colloquially, in BE, we'd say "John, put your foot down or we won't get there in time for the meeting".

#### Xavier da Silva

##### Senior Member
Thank you very much.

Is it possible to use "speed up" + "vehicle" (car, etc)? I heard it is wrong to say "speed up the car".

How is speed up used in my question above?

#### DonnyB

##### Sixties Mod
Is it possible to use "speed up" + "vehicle" (car, etc)? I heard it is wrong to say "speed up the car".

How is speed up used in my question above?
I don't think it works transitively.

You could have something like: "You need to keep within the 30 mph limit in the city, but you can speed up once you're out into open countryside."

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