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Homework Help: Newton's 1st, 2nd, & 3rd laws of motion

  1. Jan 16, 2012 #1
    a) A shirt left on your bedroom floor is still there after 2 days. (Newton's 1 law)

    b) You run into your friend while ice-skating, & you both fall in opposite directions. (3rd law)

    c) The horse you're riding trips on a tree stump & stops quickly, & you fly forward. (1st law)

    d) A baseball continues rolling until it hits the fence. (1st law)

    e) You hit a tennis ball w/ a tennis racket & the tennis ball sails over the net. (3rd law)

    f) A person jumps off a diving board. (3rd law)

    g) A swimmer swims through the water. (3rd law)

    h) F=ma (Newton's 2nd law)


    Can someone please check if I'm correct. Thank you. :smile:
     
  2. jcsd
  3. Jan 17, 2012 #2

    BruceW

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    they all look right to me.
     
  4. Jan 17, 2012 #3

    Andrew Mason

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    There is more than one correct answer here. Here is my take:

    No net force: First law.
    Net force down + collision: Second and third laws.
    No net force (ignoring gravity): First law.
    No net force (ignoring friction): First law.
    Impulse imparted to ball by racket: I = Δp = FΔt; Second law.
    Impulse imparted to diver by diving board: I = Δp = FΔt; Diver goes up and gravity brings diver down. Second law.
    Swimmer's body pushes back on water moving water backward and swimmer forward; swimmer meets fluid resistance exactly equal to push of swimmer's body on water; 0 net force so swimmer moves at constant speed through water. First and third laws apply.
    Second law if f≠0, but first law if f = 0;


    AM
     
  5. Jan 17, 2012 #4
    Thank you.
     
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