Recent content by Kikora

  1. K

    Carnot refrigerator and II law of Thermodynamics

    There is an input of work in the carnot refrigerator. The second law of thermodynamics states that heat does not flow from a cold reservoir to a hot reservoir spontaneously. However, heat may flow from a cold reservoir to a hot reservoir with the input of work.
  2. K

    Rolling solid disk

    Hi. I'm sorry for bumping this old thread. I was wondering about something in his workings. For part B, the fractional loss is not 2/3 right? 2/3 is just the loss in rotational energy. The total loss in K.E will be Initial rot. energy - final rot. energy - final translational energy? Thanks...
  3. K

    Total Energy

    I think you made a computation mistake. Because, i got the answer just fine after substituting all the values. -1.6X10^10 J
  4. K

    Total Energy

    I think he is asking you to use the easier(approximation) form of gravitational potential energy equation. (the one that involves g)
  5. K

    Total Energy

    Your radius should be in m, not km.
  6. K

    Determine mass of a glider on an air track

    You do not have to add in Fn1 and Fg1 because they cancel each other out + they are in the vertical direction. You only need to take into account the horizontal forces(which in this case is the tension from the string).
  7. K

    Jumping toy problem

    Try Using this: Elastic potential energy stored in wire or spring (Amount of work stored) * W = ½keffX2, where X is the extension of spring
  8. K

    Center of Mass Problem

    Actually, the reason why we take moments about the left person is so that we do not need to take into account of the unknown force exerted by the left person. Hence, we can solve the equation with 1 unknown(force exerted by right person) instead of having two unknowns(if you take moments about...
  9. K

    Center of Mass Problem

    The centre of mass of the couch will not move.(It is still in the middle) However, the centre of mass of the couch and the person sitting on the couch will be between the arrow(weight of the person sitting on couch) and the arrow (weight of couch). You do not have to find the new point. More...
  10. K

    Center of Mass Problem

    You are right. The total force exerted by both right and left person is 784N. What i meant was force exerted by left person is not equal to force exerted by right person. You will need to take moments about left person to find the force exerted by right person. And hence, find out the force...
  11. K

    Center of Mass Problem

    Erm. Actually, after solving for the force exerted by the right person, you'll need to find the force exerted by the left person later as well. The forces exerted by the right and left person are not equal. No. Use Taking moments about left person, Clockwise moments = anti-clockwise moments
  12. K

    Center of Mass Problem

    Eh. No. Use moments about a point. Clue: Take moments about the left person. Note: By the way, In your 3rd sentence, its "multiply this mass with gravity's acceleration" and not "multiply this weight with gravity's acceleration".
  13. K

    Center of Mass Problem

    I've drawn a free body diagram here: http://4.bp.blogspot.com/_-h5patrZ790/TP5DhJfAiNI/AAAAAAAAAV4/xFnT20VqzrI/s1600/Couch+question.PNG See if it helps u.
  14. K

    Tension on a chain.

    Since there is an acceleration, there will be a resultant force. At the fifth link, The resultant force = force exerted by fourth link on fifth link - weight of fifth link. I think you should be able to do now.
  15. K

    Buoyant forces on copper and

    Yes. That's correct.
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