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More help please

  1. Feb 23, 2005 #1
    Hey again...im back with some more...these are simple questions that just boggle my mind..maybe im just rushing myself.

    What is linear motion?
    My answer: Motion along a line

    Question: A small coin is halfway between the center and the outer edge of a turntable rotating at 45 rpm. What is the linear velocity of the coin?

    Choices Given: a) 10m/s b) 22.5m/s c) 45m/s d) Not enough information to tell
    My Answer: d) not enough information to tell

    Question: At what point will an object fall over?

    Choices given: a)When its support base is completely off the ground. b) when the center of mass is beyond the support base. c) when the center of mass is outside the object.
    My Answer: b) when the center of mass is beyond the support base.

    Question: A block of steel is attached to a block of wood. The assembly is placed on one end. Which position will be most stable?

    Choices Given: a) steel on top, wood on bottom. b) wood on top, steel on bottom. c)they are equally stable either way d) neither is stable at all
    My Answer: c)They are equally stable either way

    Question: Where is the center of mass in a donut?
    Choices Given: a) there isnt one. b)above the donut. c)below the donut. d)in the hole.
    My Answer: d) in the hole

    And one more question..is this statement correct? "Angular momentum is based on rotational inertia and angular speed?" I am sure that angular momentum is based on rotational inertia and angular VELOCITY..but could speed be said in place of velocity?

    thanks again!

    mark
     
  2. jcsd
  3. Feb 23, 2005 #2

    HallsofIvy

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    Science Advisor

    You answers are all good except this one:
    "Question: A block of steel is attached to a block of wood. The assembly is placed on one end. Which position will be most stable?

    Choices Given: a) steel on top, wood on bottom. b) wood on top, steel on bottom. c)they are equally stable either way d) neither is stable at all
    My Answer: c)They are equally stable either way "

    Go back to the third question. If the wood is on top of the steel, since steel has a higher density than wood, the center of gravity is lower. Conversely, if the steel is on top of the wood, the center of gravity is higher. Now look at what happens as the block tilts. In which configuration will a smaller angle (smaller tilt) be required to move the center of gravity outside the support area?
     
  4. Feb 23, 2005 #3
    Ah i see..so it would be more stable if steel were on the bottom, because if steel were on top, it would require a smaller tilt to move hte center of gravity out of the support area

    thank you very much,

    mark
     
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