A 20-kg girl and a boy on ice skates stand at rest facing each other. They push each other as hard as they can, and the boy moves to the left with a velocity of 2 m/s, while the girl moves to the right with a velocity of 3 m/s. (a) What is the boy's mass?

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Answer 1 · 2018-05-09T08:20:54

# "mass"_"boy"=30" "kg#

boy:

mass#=m" "kg#

#u_i=0" "ms^(-1)#

#u_f=-2" "ms^(-1)#

girl

mass#=20" "kg#

#u_i=0" "ms^(-1)#

#u_f=3" "ms^(-1)#

initial momentum#=#final momentum

#0=-2m+20xx3#

#0=-2m+60#

#=>m=30#

#:. "mass"_"boy"=30" "kg#