- #1

alberto

The goal is to close an open door in the best possible manner. You have two objects, a bouncy ball and a big chunk of sticky mud. You decide to throw one of these objects at the door to close it. The bouncy ball will bounce off the door with the same speed as it struck the door. The mud will stick to the door. Which of these two scenarios will result in the door closing with a larger speed? Use the concept of impulse in your answer.

So at first I was like "the ball", since with Impulse being the change in momentum = force x time, with the ball hitting the door and bouncing off really fast, time would have to go down in the equation, thus, force would have to go UP to compensate. But then I rationalized that if the ball is coming back off the door in the opposite direction at the same speed, it’s momentum was pretty much conserved and therefore not much was transferred to the door to shut. The mud on the other hand isn’t bouncing away, thus all of its momentum will strike the door and continue to push on the door in the same direction that the door needs to go in order to shut.

so there is definitely something wrong with one of these lines of thought....help! and thanks!