A 30 kg girl and a 25 kg boy face each other on friction-free roller blades.the girl pushes the boy,who moves?

a 30 kg girl and a 25 kh boy face each other on friction-free roller blades.the girl pushes the boy,who moves away at a speed of 1.0 m/s.the girl's speed is______m/s

A 30 kg girl and a 25 kg boy face each other on friction-free roller blades.the girl pushes the boy,who moves?
m1v1=m2v2


25*1=30*v2





25/30=v2





v2=5/6





v2=0.83m/s





BOTH move!
Reply:either...





A) they both move, because


1) she pushed him


2) his body reacted and pushed back (newton's third law)





or





B) the girl only moves if you are looking from the boy's point of view.





C) the boy only moves if you are looking from the girl's point of view
Reply:Before the 30 kg girl pushes the 25 kg boy both are at rest.





Total initial momentum of the system (girl and boy) pi=zero





when the girl pushes the boy with a force F,she experiences equal force F but in opposite direction.





the action reaction forces are internal forces, their resultant is zero.





Hence from Newton's third law, the total momentum should remain zero (i.e. initial momentum)





[momentum of 30 kg girl moving with speed v ]+[ momentum of 25 kg boy moving with speed 1 m/s] = zero





30v+25*1=zero





30v= -25





v= - 5/6 = -0.833 m/s





negative answer indicates velocity of girl 0.833 m/s is in opposite direction
Reply:5/6 of the speed of the boy (25/30)
Reply:Both move but girl is slower due to heavier weight... W= mg... More friction/ resistence
Reply:Tracy...do your own homework. You just might learn something to better yourself.





Or then again all these people could do it for you and you learn how to use others in life to do your work for you.


Ever think about law or politics?




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