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Homework Help: A two mass and spring system

  1. Apr 4, 2015 #1
    1. The problem statement, all variables and given/known data

    Two identical 0.25kg blocks (labeled 1 and 2) are initially at rest on a nearly frictionless surface, connected by an unstretched spring, as shown in the upper diagram, where x2=0.059m. Then a constant force of 17N to the right is applied to block 2, and at a later time the blocks are in the new positions shown in the lower diagram, where x1=0.01m and x3=0.108m. At this final time, the system is moving to the right and also vibrating, and the spring is stretched.

    I included a picture of the given image.

    Check all the forms of energy that change in the point particle system during this process:

    Select all that are True.
    Thermal energy.
    Spring potential energy.
    Vibrational kinetic energy.
    Rotational kinetic energy.
    Translational kinetic energy.

    2. Relevant equations
    None necessary for this problem.

    3. The attempt at a solution

    I know there is a change in translational KE because it start from rest and doesn't end at rest.

    I know there is a change in Spring PE because it initially started at rest, and ended in movement.

    I know there is a change in Vibrational KE because it initially started at rest meaning very little vibration is
    occurring and it ends in movement so that means their is an increase in Vibrational KE while PE is decreasing.

    I believe there is a change in thermal energy cause it corresponds to Vibrational KE

    I don't believe there is Rotational KE cause nothing is rotating/spinning.

    Need help... one try left


    Attached Files:

  2. jcsd
  3. Apr 4, 2015 #2
    Also, I am having troubles with this one as well.

    2) Check all the forms of energy that change in the real system during this process (assume that the vibrating spring doesn't get hot).

    Select all that are True.
    Rotational kinetic energy.
    Spring potential energy.
    Translational kinetic energy.
    Vibrational kinetic energy.

    I know there is spring PE and Translational KE, I don't think theres rotational KE cause its a spring and I think there might be Vibrational KE because it initially starts at rest and ends in motion.
  4. Apr 5, 2015 #3


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    Science Advisor
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    Vibrational energy is not necessarily considered thermal. It only rates as thermal when it is so disordered that it cannot readily be harnessed to perform useful work. A simple harmonic motion would still be considered ordered.
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