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Newtons 2nd Law of motion Practical Questions

  1. Jul 29, 2008 #1
    So i have a few questions in relation to a practical completed in grade 11 Physics

    The basic experiment about the 2nd law, in which a hanging weight is used to accelerate a cart

    the practical also had a 2nd part in which weights were added to the small cart to decrease the acceleration while keeping the hanging mass constant


    so we know F=MA

    State the relationship between the acceleration and the system mass as proportionality

    if i rearrange F=ma i get a=f/m and m=f/a

    could i answer this question with something like....

    the acceleration is directly propertional to the force when mass is constant?
    or
    The mass is directly propertional to force when acc. is constant?

    State the relationship between acceleration and acceleration force ( N ) as a proportionilty?

    another question i have is

    Why is it necassary to transfer the masses from the trolley to the mass hanger rather than simply adding more masses to the mass hanger

    im not asking for complete answers, i just seek help so those can guide me in the right direction and what i should be answering with
     
  2. jcsd
  3. Jul 29, 2008 #2
    Each of the relationship questions is asking you to compare two variables - disregard any others that are not mentioned in the question.

    For example: State the relationship between the acceleration and the system mass as a proportionality.

    The only variables given are mass and acceleration. What is the relationship between the two?

    F = MA
    A = F/M
    A = 1/M x F (this is just so you can visualize the two variables as indiviual from each other)

    Therefore, A is inversely proportional to M and is directly proportional to F. However, the question does not ask you to relate A to F. Therefore, the answer is this: The acceleration value is inversely proportional to mass value.

    Note: this is true whether or not the force is constant - all it means is that if the mass is increased, the acceleration will decrease and vice versa.


    State the relationship between acceleration and force ( N ) as a proportionality.
    Stuff you probably don't need to show:
    F = MA
    A = 1/M x F

    Stuff you definitely do need to show:
    The acceleration value is directly proportional to the force value.



    As for your last question, I am uncertain as to its intention. It asks... Why is it necessary to transfer the masses from the trolley to the mass hanger rather than simply adding more masses to the mass hanger? ...but why is it necessary to do what? I don't understand exactly what the goal of the experiment (though I have an idea) was - perhaps if I knew that it would make it an easier to answer. Could you go into more depth regarding the nature of the experiment?

    -elkface
     
  4. Jul 30, 2008 #3
    cheers mate
     
  5. Aug 15, 2010 #4
    Since you are keeping a constant system weight it is important to keep the same weight throughout the tests. By transferring the weight from the car to the hanging weights you are keeping a constant system mass, whilst changing the accelerating force.
     
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