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    I was working through the question below, and when I compared my answer to that in the back, it wasn't the same and i don't understand where I went wrong? I've italicised from where I don't understand.

    Question:
    The weight of a car is 1.8x10^4 N. It accelerates from rest to a velocity of 28ms^-1 in a time of 9.6s. Calculate the acceleration of the car.

    Answer:
    a= (v-u)/t = 28/9.6
    a=2.91 ms^-2
    m=w/g = (1.8 x 10^4)/9.81
    m= 1.83x10^3
    F=ma =1.83x10^3 x 2.91
    =5.4 x 10^3 N
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    (Original post by sabruh)
    I was working through the question below, and when I compared my answer to that in the back, it wasn't the same and i don't understand where I went wrong? I've italicised from where I don't understand.

    Question:
    The weight of a car is 1.8x10^4 N. It accelerates from rest to a velocity of 28ms^-1 in a time of 9.6s. Calculate the acceleration of the car.

    Answer:
    a= (v-u)/t = 28/9.6
    a=2.91 ms^-2
    m=w/g = (1.8 x 10^4)/9.81
    m= 1.83x10^3
    F=ma =1.83x10^3 x 2.91
    =5.4 x 10^3 N
    Ok, first of all we are given force (weight), initial velocity, final velocity, time and must find the acceleration. You gud with that....
    Now the formula for acceleration is a=(v-u)/t. So we know u =0m/s, v=28m/s and time is 9.6 seconds. Therfore chucking all them in the calculator gives acceleration= 35/12. with f=ma we only have force. So to get mass do force/g so the mass is 90000/49. Now f=ma so f=ma which is (35/12) * (1.8x10^4) which gives 53500 which in standard form is 5.4 x 10^3N. But I don't understand you get the force when the quesion asks for acceleration, you sure the question is written correctly?
    Well anyways has that helped?
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    (Original post by raman_17)
    Ok, first of all we are given force (weight), initial velocity, final velocity, time and must find the acceleration. You gud with that....
    Now the formula for acceleration is a=(v-u)/t. So we know u =0m/s, v=28m/s and time is 9.6 seconds. Therfore chucking all them in the calculator gives acceleration= 35/12. with f=ma we only have force. So to get mass do force/g so the mass is 90000/49. Now f=ma so f=ma which is (35/12) * (1.8x10^4) which gives 53500 which in standard form is 5.4 x 10^3N. But I don't understand you get the force when the quesion asks for acceleration, you sure the question is written correctly?
    Well anyways has that helped?
    that's why i'm so confused- I can use the given suvat equation to work out acceleration, so why is anything else relevant? I don't understand why you even get an answer in Newtons, when the SI unit for acceleration is ms^-2.

    My problem wasn't with the math and following what they did, but rather why it was done. thanks though!
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    (Original post by sabruh)
    that's why i'm so confused- I can use the given suvat equation to work out acceleration, so why is anything else relevant? I don't understand why you even get an answer in Newtons, when the SI unit for acceleration is ms^-2.

    My problem wasn't with the math and following what they did, but rather why it was done. thanks though!
    Isn't there a second section in the question asking about the force accelerating the car?

    if not I can't see what that bit is doing in the M/S either
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    (Original post by Joinedup)
    Isn't there a second section in the question asking about the force accelerating the car?

    if not I can't see what that bit is doing in the M/S either
    As you can see, three is no second part in the question. I'll just assume it was a printing error (5 marks for simple suvat though??)

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    (Original post by sabruh)
    that's why i'm so confused- I can use the given suvat equation to work out acceleration, so why is anything else relevant? I don't understand why you even get an answer in Newtons, when the SI unit for acceleration is ms^-2.

    My problem wasn't with the math and following what they did, but rather why it was done. thanks though!
    yh thats fine, its just I got stuck with the SI units too why acceleration was N...
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    (Original post by raman_17)
    yh thats fine, its just I got stuck with the SI units too why acceleration was N...
    Acceleration is m/s^2 or N/kg
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    (Original post by Kyx)
    Acceleration is m/s^2 or N/kg
    oh yh thanks! but, what I was told was that the answer was just Newtons so I was confused that it should be newtons per kilogram...
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    (Original post by raman_17)
    oh yh thanks! but, what I was told was that the answer was just Newtons so I was confused that it should be newtons per kilogram...
    Maybe they did the force?
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    (Original post by Kyx)
    Maybe they did the force?
    the question was probably written wrong then
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    (Original post by raman_17)
    the question was probably written wrong then
    :yes: probably, or the answer
 
 
 
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