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: 2 Basic Physics Questions

  1. Aug 28, 2007 #1
    I am very embarrassed to ask these questions because compared to other questions on these boards, these two seem very basic. Nonetheless, I have never taking physics and I am having a hard time grasping its concepts. So here are two simple questions that maybe someone could answer and explain for me. Thanks!

    1st Q: During a short interval of time the speed v in m/s of an automobile is given by v = at^2 + bt^3, where the time t is in seconds. The units of a and b should be?

    2nd Q: Suppose A = B^n*C^m, where A has dimensions LT, B has dimensions L^2T^–1, and C has dimensions LT^2. Then the exponents n and m have the values:
  2. jcsd
  3. Aug 28, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    You need to show your work before we can help-- forum rules. What do you know about the dimensions of an equation?
  4. Aug 28, 2007 #3
    To be honest, I have no idea where to start with these two questions. I was hoping someone could get me started with either one. The only thing I know about dimensions is that acceleration is Length/Time^2 and speed is Length/time. My teacher zipped through this part and the book does not seem to talk about it. In other words, i don't know much about dimensions :(
  5. Aug 28, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper

    The units on both sides of an equation must be the same.
    You can multiply/divide different units but you can only add/subtract the same units ( a bit like canceling fractions).

    so, area (m^2) = length(m) * width(m)
    or, distance(m) = speed(m/s)*time(s) + 1/2 acceleration(m/s^2)*time(s)^2
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook