Inelastic collisions with constant momentum

[haha0p1]

Homework Statement:

The total momentum before the collision in an inelastic collisions is 0, but the total kinetic energy before the collision is 1/2mv². Calculate how the total kinetic energy before collision is 1/2mv².

Relevant Equations:

Ek=1/2mv²

Kinetic energy before collision =1/2 mv² + 1/2 mv² = mv² (since energy is a scalar quantity, the direction does not matter). Kindly tell why am I not getting the required answer i.e: 1/2 mv². Am I doing the calculation wrong?

 

[BvU]

Hi,

I agree with your calculation. An unfortunate error in the book.

$\$

 

[PeroK]

It's interesting that the book specifies the "same object" or "identical" objects, where all that is required kinematically is objects of the same mass!

 

[haha0p1]

It's interesting that the book specifies the "same object" or "identical" objects, where all that is required kinematically is objects of the same mass!

Truee

 

[kuruman]

It's interesting that the book specifies the "same object" or "identical" objects, where all that is required kinematically is objects of the same mass!

I think it's economy of words. "Identical objects" is shorter than "objects of the same mass" and conveys the idea of symmetry. "Identical" becomes relatively conciser when the masses also carry equal charges.

 

[haruspex]

It's interesting that the book specifies the "same object"

No, it says "the same two objects". Presumably the same two as in the preceding question.