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Homework Help: What is the shape of a mass vs. acceleration graph?

  1. Nov 22, 2008 #1
    The mass is constant, and there is a varying force. So would the mass be the dependent value(y-axis) and the acceleration be the independent value(x-axis)?

    I think the mass is the dependent value so when I graphed it the line went straight across(horizontal). Is this right? I'm really confused because I thought acceleration was inversely proportional to mass, so it shouldn't be a linear relationship?
  2. jcsd
  3. Nov 22, 2008 #2
    You said yourself that the mass is constant. This means that for any point P(a,m) where a is acceleration and m is mass, you have the same y value (m) for any x value (a).

    This is why you got a horizontal line when you graphed mass vs. acceleration; mass doesn't actually depend on the acceleration (in this case).
  4. Nov 22, 2008 #3
    so we know F=ma right?
    Then, if your mass is constant, then the value of mass doesnt change. Its a number like 7 or 8 or 9. TO graph mass vs acceleration is to say mass on the y axis and acceleration on the X axis. So I think it should be something like a straight horizontal line like you said. This seems logical because your y-value that is mass stays constant but you acceleration changes, which is your x value. If this is what your graph depicts then it seems right. Cheers
  5. Nov 22, 2008 #4
    as mass is constant, the acceleration is a function of force only i.e. acc is directly proportional to force applied. depending the magnitude of force the acc will change
  6. Nov 22, 2008 #5
    The reason I said "in this case" was because in relativity, mass (or maybe more properly, momentum) is not constant with an increase in velocity.

    In special relativity, the relation between mass and velocity is M=\frac{m}{\sqrt{1-\frac{v^2}{c^2}}.

    Where M is the relativistic mass, and m is the rest mass. v is the velocity of the body, and c is the speed of light.

    This obviously shows that M is NOT a constant.
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