1. Not finding help here? Sign up for a free 30min 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!

Conservation of energy

  1. Dec 17, 2015 #1
    image.jpg
    I find this problem kind of tricky. I think it must be a, since a change in momentum of the car causes the same change in momentum of the earth.
     
  2. jcsd
  3. Dec 17, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That part is correct. But does that imply that the kinetic energy is the same? Compare the formulas for momentum and kinetic energy.
     
  4. Dec 17, 2015 #3
    Oh yeah! Ek=1/2*m*v^2, and v = p/m, therefore Ek= p^2/2m. Since p is the same for car and earth but the earth's mass is way bigger the kinetic energy gained by earth wud be much lower! So would option c be right?
     
  5. Dec 17, 2015 #4

    Doc Al

    User Avatar

    Staff: Mentor

    You got it. Good thinking!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted