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: Problem of Momentum

  1. Apr 14, 2008 #1
    This is an equation I found in the achieve can any one explain what this means
    ||\vec{v}_{f}||=\frac{1}{m_{1}+m_{2}}\sqrt{(m_{1}v_{1}-m_{2}v_{2}\cos(30))^{2}+m_{2}^{2}v_{2}^{2}\sin^{2}(30)}
    here is the problem Dan is gliding on his skateboard at 3.00 m/s. He suddenly jumps backward off the skateboard, kicking the skateboard forward at 8.00 m/s (as measured by an observer on the ground). Dan's mass is 40.0 kg and the skateboard's mass is 5.00 kg. How fast is Dan going as his feet hit the ground?
    I am just not sure which equation to use.
     
  2. jcsd
  3. Apr 14, 2008 #2

    Hootenanny

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Forget equations, they're hard to memorise in the first place :rolleyes:. Instead, think about the concepts involved. Which concept(s) do you think are important here?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook