After a flipped video looking at inertia, I decided to get the class to participate in a small experiment testing Newton’s first law. In an ideal world, I wanted the plate to be whipped away in a straight line. This would have demonstrated that with no other external force acting upon the egg (besides gravity), the egg would drop into the cup.
As you can see in the video, the student pulled the plate on an angle resulting in the egg missing the cup!! (My wife after viewing the video said to me “Fail sir!). But with a little bit of questioning, the students established that when the plate was pulled on an angle, it caused the cardboard roll to exert an external force onto the egg, changing it’s downward path and causing it to miss the cup. Not really a fail after all!