- Debatable answers

Some time ago I posted about the Physics Question of the Week (PQW) website. A very interesting site, with questions and answers (videos for anyone to believe). Recently, I was showing my classmates (other grad students) some of these questions and there was a huge uproar about some of the answers given on the website. For example, look at this question, the answer is on the site but I invite you to try to answer it on your own first. After that, look at the answer and tell me if you agree. From their answer I understand that the same thing will happen no matter what spring (k-constant value) and what mass are used, as long as the initial setup looks the same, that is, the mass is sufficiently large to stretch the spring outside of the cup and the spring is strong (or weak) enough to balance the weight.

Among my friends, the biggest debate was that we could visualize situations in which we think a different thing will happen. I should admit though that I agree with the video.

By the way, I was told that the Professor in charge of PQW has asked these questions to many Assistant, Associate and Full Professors, including Nobel Laureates and supposedly they don't all get them right. So, don't feel bad about getting it wrong either.