[单选题]
You (50-kg mass) skate on ice at 4.0 m/s to gre4 f07 lann7a2 li;p -fbcl1fkret youmb: 12cx 7xr qyxwpv53r friend (40-kg mass), who is standing still, with open arms. As you collide, whicb3m:51xx w xrpqv72yle holding each other, with what speed do you both move off together?
