Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: True or false : I want check my answer please

  1. Aug 29, 2010 #1
    True or false :

    It is possible to have motion in the absence of a force (F)
    beacuse no motion without force

    If an object is not moving , no external force acts on it (T)
    beacuse each object will not move unless a force acts on it

    If a single force acts on an object , the object accelerates ( T)
    beacuse every object has force has accelerates

    If an object experiences an acceleration , a force acts on it ( T)
    beacuse every object has force has accelerates


    If an object experences no acceleration , no external force acts on it ( T)
    beacuse every object has no force has no accelerates

    If the net force acting on an object is in the x direction the object moves in the x direction ( T )
    beacuse when force effet on the object will go same direction of force

    I want check my answer please >>


    3. The attempt at a solution
     
    Last edited: Aug 29, 2010
  2. jcsd
  3. Aug 29, 2010 #2

    phyzguy

    User Avatar
    Science Advisor

    By my count you have 2/6 correct, 4/6 wrong. Think about the difference between velocity and acceleration.
     
  4. Aug 29, 2010 #3

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It would be much easier to help if you explained your reasoning.
     
  5. Aug 29, 2010 #4
    I explained my reasoning by apply newton second law
     
  6. Aug 29, 2010 #5

    jgens

    User Avatar
    Gold Member

    Why don't you explain what you think motion means? The term appears in a number of problems that you got wrong, so you might want to be more specific about things.
     
  7. Aug 30, 2010 #6
    I get the similar count as phyzguy. Try explaning the reasoning to each prob .. exactly why you chose whether true or false.
     
  8. Aug 30, 2010 #7
    ?????
     
  9. Aug 30, 2010 #8

    HallsofIvy

    User Avatar
    Science Advisor

    Do you not know what "explain" and "reason" mean?
     
  10. Aug 30, 2010 #9

    HallsofIvy

    User Avatar
    Science Advisor

    I can't imagine how you would answer these "true" or "false". Many of them simply don't make sense.

    The 'because' seems to contradict the statement!

    Again, a non-sequitur. "because each object will not move unless a force acts on it" would explain "if an object is moving there must be an external force acting on it", not the statement given.

    Okay- not very good English, but true.

    Once again a "p implies q because q implies p" statement. Not logical.


    The statement is true but because of "every object that has a force accelerates" not the reason given here.

    [qote]If the net force acting on an object is in the x direction the object moves in the x direction ( T )
    beacuse when force effet on the object will go same direction of force [/quote]
    True

    Most of these seem to be of the form "if p then q because if q then p" (which is false logic). Also, as others have tried to point out, an object can move in a straight line, at constant speed, with NO force on it. You don't seem to realize that.
     
  11. Aug 30, 2010 #10
    but all my answer are correct ??
     
  12. Aug 30, 2010 #11

    jgens

    User Avatar
    Gold Member

    Halls, I assumed that the "because ..." following each question was his/her attempt at justifying the answer (T/F) that he/she gave for the statement above that line. If that's the case, then the questions make sense, it's just that the OP's explanations don't.
     
  13. Aug 30, 2010 #12

    jgens

    User Avatar
    Gold Member

    Most of your answer are not correct if you've correctly transcribed each statement.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook