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: Physics 11 help please ?

  1. Dec 15, 2008 #1
    1. The problem statement, all variables and given/known data

    A 55 kg student wearing skates stands at rest on a frictionless horizontal ice surface. She throws a 10 kg backpack horizontally with a speed8.3 m/s .
    What is the velocity of the student after she throws the backpack?

    2. Relevant equations

    F[tex]\Delta[/tex]t = m[tex]\Delta[/tex]v

    3. The attempt at a solution
    so the answer should be 1.5 m/s [N] and i got this by dividing 10 kg (backpack) by 55 kg (student) and then multiplying that answer by 8.3 m/s . is this the right way or is there a proper formula i should follow?
    thanks !
  2. jcsd
  3. Dec 15, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That's correct. The impulse given to the backpack will be exactly equal and opposite to the impulse given to the student. Thus:
    mstudent*vstudent = mbackpack*vbackpack

    Just solve for vstudent.
  4. Dec 15, 2008 #3
    great, thanks ! :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook