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: Mechanical Physics: Momentum

  1. Feb 27, 2008 #1
    1. The problem statement, all variables and given/known data


    A car of mass 1000kg moving with a speed of 10m/s has head on collision with a truck of mass 2000kg moving in the opposite direction with a speed of 5m/s. After impact the car moves with a speed of 2m/s in the opposite direction to its original motion.

    1 Calculate the rate of change of momentum of the car if the impact lasts for 0.25 sec

    2 what is the force that the car exerts on the truck during impact. State the laws.

    3 Find the velocity of the truck after collision

    2. Relevant equations

    No equations given

    3. The attempt at a solution

    1: Mv- Mu
    1000 * 10 - 1000* -2 = 12000/0.25 = 48 000 N

    2: For every action there is an equal and opposite reaction so 48000 N

    3: dont have a clue :(
  2. jcsd
  3. Feb 27, 2008 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes there are. Look up "conservation of momentum" and "impulse".

    You've got the units wrong. If you multiply mass times velocity, you get a momentum, not a force. But even after correcting that, it gives you the change [itex]\Delta p[/itex] in momentum. You were asked for the rate of change [itex]\Delta p / \Delta t[/itex] of the momentum.

    Again, look up "impulse" in your book.

    For this one, look up "conservation of momentum" in your book.

    Try to implement my advice in another solution attempt. If you're still stuck, then repost.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook