accelerate vs speed up

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  • Egmont

    Senior Member
    English - U.S.
    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.
     

    Parentheses

    New Member
    English
    "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
    English
    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.
     

    DonnyB

    Sixties Mod
    English UK Southern Standard English
    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". :)
     

    DonnyB

    Sixties Mod
    English UK Southern Standard English
    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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