When heather grabbed the glass of ice water, the ice cubes were floating at the top. why were the ice cubes floating in the water?

The ice cubes were floating in water because they are less dense than liquid water. When water is frozen, a structure that is crystalline is formed that is held by hydrogen bonding. Due to the orientation of these bonds, the moleules would push far away from each other causing it to have a bigger volume and a lower density.

Two cars collide, lock bumpers and move together after the collision.this collision is known as perfectly inelastic collision.