Lesson 4: Test your Knowledge on Laws of Motion – Part 7

Scene 6: Hancock Stop the Train 

Watch a scene from the movie “Hancock” where the hero stops a train without moving a step. Try to answer the following questions:

What Laws of Motion are broken?

Give a breakdown of the circumstances in the scene in relation to the equation Force equals mass times acceleration (F = ma).

According to the Second Law, which had the higher force, Hancock or the train?

How does this scene defy the Third Law of Motion?

https://www.youtube.com/watch?v=NLRNYIT42ig 

Click here to read a discussion on the scene and compare your thoughts.

This scene illustrates the Second and Third Newton’s Laws of motion. In this scene the train is stopped in its tracks by superhero bum Hancock. Consider the damage done to the train. Again, like in the Twilight scene, there is no visible acceleration by Hancock and his mass is MUCH smaller than the trains. This means that the F=ma of Hancock is much smaller than the F=ma of the train. Therefore Hancock should have been overcome by the train’s force and gotten ran over. Now consider the Third Law of Motion, for every acting force there is a reacting force. In this scene, the acting force on the train is strong enough to stop it completely and warp its surface. However Hancock appears to not react at all, which means that there was no opposite reacting force from the train to him. According to the conservation of momentum, if the train came to a stop, then all the momentum it had would have been transferred onto Hancock, yet this was not the case.