Imagine 2 cars colliding head-on. How do Newton's 3rd law and the concept of equal and opposite forces explain what happens to both cars during the collision?

Answer 1

When two cars collide head-on, Newton's Third Law of Motion comes into play, which states that for every action, there is an equal and opposite reaction. This principle helps to explain the dynamics of the collision.

1. Action and Reaction Forces: As the two cars collide, each car exerts a force on the other. For example, if Car A exerts a force on Car B (as they crash into each other), Car B exerts an equal and opposite force back on Car A. These forces are equal in magnitude but opposite in direction.

2. Impact on Both Cars: Because of this interaction, both cars will experience a change in momentum as a result of the collision. The magnitude of each car's force, determined by their mass and speed just before the collision, influences how each car will respond to the impact:

   • Car A: If Car A is significantly heavier or moving faster than Car B, it will experience less acceleration (change in speed) compared to Car B, according to Newton’s second law (force = mass × acceleration).
   • Car B: Conversely, Car B, being lighter or slower, may experience a greater degree of acceleration (or deceleration) upon impact.

3. Deformation and Damage: The forces involved will also cause physical deformation to both cars. The structural integrity of the cars will absorb some of the energy transferred during the collision. The stronger car may suffer less visible damage, while the weaker car may sustain significant deformation and potential damage.

4. Momentum Transfer: Additionally, momentum is conserved in the system (assuming no external forces). The total momentum before the collision equals the total momentum after the collision, factoring in the forces acting between the two vehicles. Depending on their masses and velocities, this can lead to various outcomes in terms of post-collision trajectories.

In summary, when two cars collide, Newton's Third Law means that each car experiences forces that are equal in size but opposite in direction, leading to changes in speed and direction for each car as well as possible physical deformation, illustrating the fundamental principles of action and reaction in the context of motion and forces.