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Thread: Fun Physics Quiz question

  1. #1
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    Fun Physics Quiz question

    **** As the OP I am asking for NO Googling on this ****

    Answer this from your own head to keep it fun and fair for all.


    A guy is sitting in a little fishing boat on a pond.

    He is holding a common brick in his hand.

    If he drops the brick into the pond... Will the water level go down, go up, or stay the same ?


    Not a silly trick question in any way.

    And if you post w an answer, you have to EXPLAIN the answer.

    The correct and full explanatory answer is very brief, only takes like one or two sentences.

    I'll be around here today and will holler when we have a Winner !

    Marc
    Last edited by Marc Jeske; 07-27-2019 at 4:27 PM.
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  2. #2
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    When the brick is released from the hand of the person in the boat there may be a slight, immeasurable drop in the water level due to less water displacement by the boat. When the brick hits the water it would depend on whether the density of the brick displaced more water by being in the boat or if its size is equal to the amount of water it displaced while in the boat.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  3. #3
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    Common everyday ordinary masonry brick.

    And, of course, whatever water level change there may be it will be very small, BUT still a technical change.

    Jim - Please answer again.

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  4. #4
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    In the boat, the brick is displacing its weight in water. In the water, the brick is displacing its volume in water, but since it's heavier than water, and no longer displacing its weight in volume, from when it was in the boat, the water level will go down.

  5. #5
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    Actually, on re reading Jim's answer, I declare him the Winner !!!!!!!

    And actually he went above and beyond by mentioning the brick in the air time period.

    Shows full understanding !!!!!!!

    So, ya... a normal common brick will displace more water by weight, than by volume.

    So the water level is highest when the brick is in the boat.

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  6. #6
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    Tom - Yup !

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  7. #7
    Wouldnt the water level stay the same?

    When the brick is in the boat, wouldnt the water go up because the boat is a little heavier, pressing down on the water more than if the brick werent there, raising the water level very slightly more than if the brick werent in the boat? When he throws the brick into the water, the boat is lighter and presses down less on the water. But now the brick is on the bottom, which raises the water very slightly - back to where it was when it was in the boat? (It's the same brick in the boat or in the pond.)

    I hope this makes sense.
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  8. #8
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    Frederick - You are thinking good... but realize the brick will displace more water by it's weight, than it will by it's volume.

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  9. #9
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    Great job Guys !!! that was quick !!!!!!

    Marc
    I'm pretty new here, not as as experienced as most. Please don't hesitate to correct me

  10. #10
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    When he throws the brick into the water, the boat is lighter and presses down less on the water.
    If he throws the brick with an upward projection, the reaction of the motion will press the boat down momentarily.

    There can be a lot of things going on in this situation. There can also be very little going on.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  11. #11
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    Reminds me of the David Letterman skit "Will it Float?". If the brick sinks the water level goes down. If it floats or has neutral buoyancy the water level stays the same. The water level never goes up.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  12. #12
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    Since the brick is denser than water, it will displace less water when itís in the lake than in the boat.

    The water level in the lake will fall once the brick is transferred from the boat to the lake.....Rod

  13. #13
    stay the same
    Last edited by Jim Allen; 07-27-2019 at 6:37 PM.
    Best regards,

    Jim
    Lakeside, Oregon

  14. #14
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    Now, if you drop that brick on your foot, you may have a very different answer...one that you can't post here. LOL
    --

    The most expensive tool is the one you buy "cheaply" and often...

  15. #15
    Unless your trying to sink something you don't want found, why do you need a brick in the boat?

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