A 30kg girl and a 20kg?

A 30kg girl and a 20kg boy face each other on friction-free roller blades. The girl pushes the boy, who moves away at a speed of 1.0m/s. The girls speed is _____ m/s.


a. 0.45


b. 0.55


c. 0.83


d. 1.2

A 30kg girl and a 20kg?
While momentum seems a logical place to start, if one uses the definition of momentum being m*v, it looks like the girls speed would be 2/3 of the boys (unless I totally misunderstand the whole issue, a definite possibility) however, 2/3 of 1, (0.66) is not a choice.





Using calculations for kinetic energy, I come up with 0.816, which also isn't a choice, but is sort of close to (c) 0.83





Maybe the links below will help you, or maybe someone who actualy knows will answer.
Reply:use momentum to figure it out
Reply:When you are talking about friction free surface, there are no 2 ways about it. It is conservation of momentum.





m1v1 = m2v





Use this equation.



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