Which word is described by this riddle poem. (hint: jails and phones) my first is in cars but isn't in bars my second's in dance, but not in pants my third is in lame, my fourth is the same. what word could i possibly be?

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. when the carts collide, they hook together. assume that positive momentum is to the right. which graph best represents the momentum of both carts over time, before and after the collision?