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!

PLease help on these 2 questions (momentum-impulse fans here)

  1. Feb 6, 2005 #1
    Please help

    An astronaut , 80 KG, is carrying a bag which is 20 KG, walking at a speed of 2 M/S toward a station, He throw the 20 KG bag forward at 6 M/s, what is his final velocity and direction(away from station, toward station)

    heres another one

    an astronaut is walking at .15 M/S toward a station, he wants to stop, he throws a 2.5 KG rock toward the station , what does a speed of the rock have to be in order for him to stop, thanks

    :tongue: :tongue2: :biggrin: :rolleyes:
     
  2. jcsd
  3. Feb 6, 2005 #2

    Galileo

    User Avatar
    Science Advisor
    Homework Helper

    The total momentum is always conserved.
    Before the astronaut throws the rock, the total momentum is:
    [tex]p=(m_a+m_b)v[/tex]
    where [itex]m_a[/itex] is the mass of the astronaut and [itex]m_b[/itex] the mass of the bag.
    What is the total momentum after the astronaut has thrown the rock?

    Same reasoning applies to the second question.
     
  4. Feb 6, 2005 #3

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    Galileo,u mixed the bag with the rock and hence the problems :tongue2:

    Now,after the precious indications given,which could have been put into 4 simple words "APPLY CONSERVATION OF MOMENTUM",what are the results...?

    Daniel.
     
  5. Feb 6, 2005 #4

    Curious3141

    User Avatar
    Homework Helper

    Apply conservation of momentum, taking care to make sure the signs of the velocities are consistently applied. And show your thoughts and working first.
     
  6. Feb 6, 2005 #5
    i am having trouble finding the final velocity of the astronaut though
     
  7. Feb 6, 2005 #6

    Curious3141

    User Avatar
    Homework Helper

    In the first problem, take the direction of travel toward the station as positive.

    What is the initial momentum of the astronaut-bag combo ?

    What is the final momentum of the bag ?

    Therefore what is the final momentum of the astronaut ? Hence what is the final velocity of the astronaut ?

    Do the second problem with the same basic principles.
     
  8. Feb 6, 2005 #7
    WHAT Formula should I use
     
  9. Feb 6, 2005 #8

    Curious3141

    User Avatar
    Homework Helper

    Do you mean to say that you don't know the definition of momentum ? You've never learned [itex]p = mv[/itex] ?
     
  10. Feb 6, 2005 #9
    is the answer to the first [roblem 4 m/s backwards
     
  11. Feb 6, 2005 #10

    Curious3141

    User Avatar
    Homework Helper

    That is not correct. Show the working please.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: PLease help on these 2 questions (momentum-impulse fans here)
Loading...