Need help with a Physics question?

Discussion in 'Community' started by iJon, Mar 11, 2003.

  1. iJon macrumors 604


    Feb 7, 2002
    My friend needed some help with this problem and since i took physics last year i have forgotten some stuff and im lazy to figure it out. i thought why now ask you guys because you are all really smart (or at least most of you). here it is

    "A cart with a mass of 114 kilograms starts from rest and travels 4.7 meters in 2.5 seconds. The cart is uniformly accelerated during this time. What is the net force acting on the cart?"

  2. Mr. Anderson Moderator emeritus

    Mr. Anderson

    Nov 1, 2001
    ah, the old homework thread rears its head - someone posted a Math problem a while back ;)

    Haven't had physics in 10 years, I'd have to go look up the equations, but its a straightforward problem. I'd suggest he go do the looking up and find a simillar problem and figure it out himself, he'll remember more and when something like this is on the test, probably do better.

  3. Zeke macrumors 6502a

    Oct 5, 2002
    Greenville, SC
    Formula for constant acceleration is:

    x = (1/2)*a*t^2


    F = ma

    You have position traveled (x), time (t) and thus you have a. From that you can find F.
  4. chibianh macrumors 6502a


    Nov 6, 2001
    hey! maybe i should come here for help with some of my modern physics!
  5. Over Achiever macrumors 68000

    Over Achiever

    Jul 22, 2002
    Toledo, OH, formerly Twin Cities, MN
    I'm a physics major, astrophysics major, and math major, and a biology and chemistry minor. Oh and did I mention I'm a pre-med?:p I'm graduating this I'm fairly in tune w/ the sciences right now. Lemme know if you have any questions.

    I'm ok in:
    Classical physics (kinematics, electricity and magnetism)
    Modern physics (quantum, thermal, relativity)
    General, organic, physical, analytical chemistry
    Biology (plant, animal, cell), genetics, biochemistry
    anything about astronomy or math
    plus some other stuff (C++, etc.) that i can't remember right now

    :D :D :D

    See why i'm an over achiever? :p
  6. King Cobra macrumors 603

    Mar 2, 2002
    How much time do you have on your hands, again? :)

    Well, I'm in Honors Physics, and working on keeping my average for the class at or above a 90%.

    When working with Physics and forces, knowing the formulas is important. But knowing how to derive many formulas will also be very helpful.

    Also, when working with multiple unknowns, basically, it comes down to substitution. You can do this by using simple algebra with variables.

    My first H. Physics teacher (there have been three different H. Physics teachers for our class this year) told our class something very helpful in making sure you have the right answer. Check to see if your units work out. Also, before you actually put in numbers in your calculator to solve, approximate first. If these steps check, you most likely will have the right answer.
  7. Kwyjibo macrumors 68040


    Nov 5, 2002
  8. Steradian macrumors 6502

    Dec 3, 2002
    San Jose

    I wanna try to stay on topic but...How is physics "easy" I am taking I.B Physics HL 3-4 and it is quite difficult...Kinda like a second math class in some respects... O yeah and ijon, does your friend with the physics problems have a mac w/ OS X cause thier is a great program called Physics 101 it would be useful for problems like the one that he had "trouble" with...
  9. iJon thread starter macrumors 604


    Feb 7, 2002
    Re: well...

    actually to tell you guys the truth the guy was me. i just felt like an idiot asking such a dumb question. physics has never been my strong point and probably never will be. plus the way my teacher teaches its hard to learn. my friend who knows a ton about physics wasnt here today to help me and my other friend so i was kind of screwed. But i remember how smart most of you are, just like over achiever. thanks for the help guys and thanks for the program, im gonna go check it out right now. try not to laugh at me too much, but i can honestly say i have much stronger fields than physics at my age of 17.

  10. lmalave macrumors 68000


    Nov 8, 2002
    Chinatown NYC
    Holy cannoli, Over Achiever! Among those which subject do you prefer? I guess you lean more toward biology/biochem if you're premed.

    I myself was a Physics major for a couple years before I got my ass kicked. I whimpered away with my tail between my legs and ended up getting an Electrical Engineering degree with a heavy Physics slant (physics of semiconductors etc). Not that the Physics was over my head or anything - but the competition was just too much. I used to think I was a smart cookie until I met some real geniuses :eek:

    Still like Quantum Physics, though. Every now and then I go back and read the postulates of Quantum Mechanics from my old textbook so I can recapture some of that exhiliration of figuring out how the world really works. :)
  11. lmalave macrumors 68000


    Nov 8, 2002
    Chinatown NYC
    Re: Re: well...

    My suggestion is this: as you go through the class make a sheet of all the formulas you come across. When you have to do homework, the answer will be somewhere in the formulas. Then it's just a matter of figuring out which formula you need and doing the algebra (or calculus, for more advanced physics).

    Physics just comes down to math, even for more advanced subjects. Even Einstein, when he was developing his theories, would just start with basic assumptions, then just do the math and see where it led him. Einstein derived his entire theory of Special Relativity by just taking the already commonly known physics formulas, then making the bold assumption that nothing can travel faster than light in a vacuum, and then just seeing what math came out of it...
  12. iJon thread starter macrumors 604


    Feb 7, 2002
    Re: Re: Re: well...

    thanks for the help. that would probably be a good idea, keep a list of all forumlas. im gonna play with that physics program. our teacher feels we should be able to use anything we can use to make physics easier, not just using pen and paper. and since i have a 12 inch powerbook now i can whip it out in class and see if it helps me. there is lots of encouragement at this site and i thank you guys for helping me out, especially you people who have like a bazillion degrees in physics.


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