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: How to calculate tension

  1. Mar 30, 2009 #1
    hi i am in grade 11 university physics, and i have a test coming up that requires me to calculate tension. Unfortunately i have no clue how to do this. Can someone help ?
  2. jcsd
  3. Mar 30, 2009 #2


    User Avatar
    Homework Helper

    well it depends on the question you are given. But I'd say (at a random guess) that you need to resolve all the forces in one direction and put that equal to ma, then try to solve from there.
  4. Mar 30, 2009 #3
    ok well my question states that, two toy ducks are attached by a string. the front duck has a mass of 5 kg, and the back duck is 2.0 kg. they are bing pulled wiith a force of 10N and there is no friction.
    calculate the tension of the rope after u have calculated the acceleration.

    the acceleration of the ducks is 1.4m/s2
    and i drew an FBD like soo


    i still dont kno where to go from here?
    Last edited: Mar 30, 2009
  5. Mar 31, 2009 #4


    User Avatar

    Homework .. ehh

    First u have to calculate the accelaration of the system:

    F=m(total)*a => a=F/m(total)

    m(total)=m1+m2=7 kg

    the Tension is equal to the inertial force that the second weight (2kg) exerts. so:


    m2-second duck 2 kg
  6. Mar 31, 2009 #5
    thanks a lot, that helped me tremendously. :)

    i get it now, but there is another part where it says that another duck(1 kg) is added, and it is put at the front of the row.


    Now it asks for the tension connecting ducks 2(2kg) and 3(1kg)and then the tension of ducks 1(5kg) and ducks 2(2kg) . would the tension still be equal to the inertial force of the last duck(2kg)? or would it now be equal to the inertial force of the middle duck(5kg)?
    Last edited: Mar 31, 2009
  7. Mar 31, 2009 #6


    User Avatar
    Homework Helper

    In all these questions, once you have determined the acceleration for the group, then the tension (or force in between if it is pushing it) will necessarily be the acceleration times all the mass that is being pulled (or pushed as the case may be.)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook