When 2 objects of the same mass traveling at the same speed collide is the energy canceled out?

Answer 1

The answer depends on the material of the objects. In physics, one useful concept is the concept of a perfect elastic collision, which is an idealization of the real world. An elastic collision is a collision where no deformation of objects is taking place, and thus the kinetic energy of the moving objects is preserved as no kinetic energy is transformed to heat or work during an elastic collision. In short, for elastic collisions, kinetic energy is preserved and not canceled out. In reality, there will always be some (or a lot) loss of kinetic energy to heat or work done in deforming objects, think of a car crash where there is a lot of kinetic energy spent in deformation of the cars (modern cars are designed to absorb a maximum amount of kinetic energy to be converted into deformation of objects in order to save lives), but in practical life there are many situations where the fraction of kinetic energy lost to heat or work during a collision may be neglected as it is very small. A good demonstration in real world is colliding billiard balls, or the stones used in the sport of curling, these kind of collisions may for practical purposes be considered elastic. The sum of kinetic energy and the sum of momentum for the moving objects are the same before and after the collision. This means, if 2 equal objects of same mass and same speed but opposite direction of movement collide head on in an elastic collision, their direction of movement will be reversed and their speed will be the same as before collision. Think of two equal billiard balls travelling at same but opposite speed colliding head on. When a moving object hits a moving object at an angle, or at rest or travelling at different speed or is of different mass, that is a different story, but the same rules of physics apply of course, the speed and directions of movement of the objects after any elastic collision may be easily calculated using Newton's laws.