The Dress That Turns into a Coca Cola Machine 

    This specially designed dress looks like a normal dress，but if you unfold it and cover yourself，you may look like a Coca Cola vending machine（自动售货机）. Because there are many vending machines like that on the street，it must be easy for you to hide．If you feel that someone is following you or there is some danger，you can disappear within five seconds．But don't use it to scare your classmates．That'll be rude.
                                  

    The M-Dress is a nice black dress．It is also a mobile phone．It accepts a standard SIM card and allows the wearer to receive calls without carrying an actual(真实的) phone in their pocket or purse．You just need to bring your hand to your ear when you want to answer a phone call．When you finish talking and release your hand，the call will close．It is fashionable and useful．But it will certainly be an embarrassing moment when your dress rings in public．
  Air Conditioned Jackets 

    You will love these air-cooled jackets in summer time when it is very hot outdoors．The jacket has fans that draw air in．The fan is powered by an inside battery．Now it is possible to spend nearly every second of your day with cool air．

如图所示，B、C、D、E、F，5个小球并排放置在光滑的水平面上，B、C、D、E，4个球质量相等，而F球质量小于B球质量，A球的质量等于F球质量．A球以速度v₀向B球运动，所发生的碰撞均为弹性碰撞，则碰撞之后（   ）