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Homework Help: Test corrections

  1. Oct 31, 2011 #1
    Test corrections!!!!

    1. The problem statement, all variables and given/known data
    1.) a railroad car of mass m is moving with speed v when it collides with and connects to a second railroad car of mass 3m, initially at rest. how do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision.
    speed/Kinetic Energy
    b.)less,the same​
    c.) the same, less​
    d.) greater, the same​

    2.) a ball of mass m and momentum p has kinetic energy equal to which of the following?
    a.) 1 p2/2 m​
    b.) p2/m​
    c.)2 (p2/m)​

    3.) a new planet is discovered that is twice the Earth's mass and twice the Earths radius. On the surface of this new planet, a person who weights 500N on earth would experience a gravitational force of
    2. Relevant equations

    3. The attempt at a solution
    1 is not b
    2 is not b
    3 is not c
  2. jcsd
  3. Oct 31, 2011 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Re: Test corrections!!!!

    What have you tried?

    Where are you stuck?

    Can you give any reasons as to why the listed answers are wrong?

    A hint for #2: What is the formula for p? Pk\lug that formula in for p in the four choices. See if any of them result in the formula for kinetic energy.
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