Questions: A group of students measure the mass and velocity of two cars before and after they collide. Which of the following will the students be able to demonstrate? The total momentum of the two cars will increase after the collision. The total momentum of the two cars will decrease after the collision. The momentum of each car will stay the same before and after the collision. The total momentum of the two cars will be the same before and after the collision.

Solution Steps

Momentum is a vector quantity defined as the product of an object's mass and velocity. In a closed system, where no external forces are acting, the law of conservation of momentum states that the total momentum of the system remains constant before and after a collision.

1. The total momentum of the two cars will increase after the collision.
   This statement contradicts the law of conservation of momentum, as momentum cannot increase in a closed system without external forces.

2. The total momentum of the two cars will decrease after the collision.
   Similar to the first option, this statement is incorrect because momentum cannot decrease in a closed system without external forces.

3. The momentum of each car will stay the same before and after the collision.
   This statement is incorrect because, in a collision, individual momenta of the cars can change, but the total momentum of the system remains constant.

4. The total momentum of the two cars will be the same before and after the collision.
   This statement is correct according to the law of conservation of momentum, assuming no external forces are acting on the system.

Final Answer