1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Accelerometer question

  1. Mar 5, 2016 #1
    1. The problem statement, all variables and given/known data
    A small mass m hangs from a thin string and can swing like a pendulum. You attach it above the window of your car. When the car is at rest, the string hands vertically. What angle θ does the string make when the car accelerates at a constant a=1.20m/s^2?

    2. Relevant equations
    I assume a relevant equation is ƩF = ma

    3. The attempt at a solution
    This is already solved in my book but I was trying to do it by myself

    I know I need to find ƩF = may and ƩF = max

    And I know that ƩF = may is FTcosθ -mg=may

    And that ƩF = max is FTsinθ =max

    My book says that FTcosθ -mg =0, and my question is why???? is ay=0? How can I know that?
  2. jcsd
  3. Mar 5, 2016 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Presumably the car is accelerating horizontally, not vertically.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted