Kinetic energy and momentum of two objects

  • Thread starter wilmerena
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  • #1
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do 2 objects that have the same kinetic energy necessarily have the same momentum? I cant think of a simple example :yuck:
 

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  • #2
AKG
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wilmerena said:
do 2 objects that have the same kinetic energy necessarily have the same momentum? I cant think of a simple example :yuck:
Consider a 5 kg mass going at 50 m/s, thus having 6.25 kJ of kinetic energy. Now, a mass of 125 kg going 10 m/s also has 6.25 kJ of kinetic energy. However, the first object has a momentum of 250 kg*m/s, and the second has 1250 kg*m/s of momentum.
 
  • #3
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thanks so much =o) !!
 
  • #4
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what if they both have 0 momentum, so does it follow that the kinetic energy of the system doesnt have to be zero as well? or does it?
 
  • #5
Doc Al
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wilmerena said:
what if they both have 0 momentum, so does it follow that the kinetic energy of the system doesnt have to be zero as well? or does it?
Think about it. For a simple object:
[tex] KE = 1/2 mv^2[/tex]
[tex] momentum = mv[/tex]
The only way an object can have zero momentum is if its speed (v) is what? Then what is its KE?
 
  • #6
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thanks again, i think i just spaced out on that one ;oP
 

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