Please tell the correct answer​

1.what is where an object is located 2. what is how fast an objects speed is changing 3. what is how fast an object is moving

The speed of light can be used to measure the

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •