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!

Collision and conservation of energy

  1. Mar 7, 2013 #1
    I wanted to check some concepts in collisions because I'm a little bit confused.

    In a real-world collision (Where everything applies, friction and so on) conservation of momentum doesn't really apply because there is friction, which is an external force.

    1)That is the only reason momentum isn't conserved, right?

    Moving on, mechanical energy isn't conserved either, because there are non-conservative forces (that is, friction plus energy conversion to sound/heat)

    2)And those are the only reasons mechanical energy isn't conserved, right?
  2. jcsd
  3. Mar 7, 2013 #2
    Energy is ALWAYS conserved just in different ways. (Conservation of energy)
  4. Mar 7, 2013 #3
    Yes, sorry. I meant in the system block 1 + block 2, supposing a collision between two blocks.
  5. Mar 7, 2013 #4


    User Avatar
    Science Advisor
    Homework Helper

    Yes, mechanical energy can be lost to heat etc. Momentum is ALWAYS conserved. The only way you can lose it is by tranferring it to something else. In the case of friction it's just transferred to the object you are rubbing against. That's Newton's third law.
  6. Mar 8, 2013 #5
    Thanks. Also, I think I should start saying 'Mechanical energy is transformed' and Momentum ins transferred' instead of 'Lost' as I was saying.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted