Monday, November 11, 2013

play ball

Friday's FCIS Keynote speaker was Harvard Physics Professor Eric Mazur.  His talk, entitled "Confessions of a Converted Lecturer" was in line with the current thinking on the flipped classroom.  His thoughts are that education is not simply a transfer of information, but that students must actually assimilate this information in order to both retain and use it effectively.  The flipped classroom is one idea that allows students to transfer the information at home by watching lectures, but then assimilate it in the classroom through problem solving, debate, discussion, and a wide variety of other learning tools. 

In the talk he outlined a 6 - step process by which teachers might effectively get students to assimilate information.  He suggested that teachers

1.  Ask students a question
2.  Give them time to think
3.  Take a poll of student answers
4.  Allow the students to discuss their answers
5.  Repoll the students
6.  Explain the solution or have a student explain

This is not the first time I have heard about this technique.  At another conference, the speaker used it with the question below.  It is a favorite in my calculus classes and in my summer training sessions for calculus teachers.  It stumps my students quite a bit, and many teachers as well, but then we discuss it and you can literally see lightbulb go on.  We cannot follow Mazur's model very easily here, but the method and the question are worthy of discussion. 

Think about a ball you have thrown into the air and consider the ball at the exact moment that it reaches it's greatest height.  At that exact moment, which of the following statements is true?   

A.  The velocity and the acceleration are the same.
B.  The velocity is greater than the acceleration.
C.  The acceleration is greater than the velocity.
D.  There is not enough information to know the answer. 

What do you think?

  • Can you explain your answer in a mathematical way?
  • Can you explain your answer so that a middle school student can understand?
  • What do you think of this model for the classroom?
  • Have you used it and if so, could you share your questions?

I will post the answer at the end of the day if the discussion does not reveal it.

You can learn more about Eric Mazur and his work here

Photo Credit


  1. When the ball is at it's maximum height. It must stop for a moment so it's velocity is zero. The acceleration due to gravity on earth is always pulling us down and is thus negative. As a result the velocity is greater than the acceleration and the answer is B

  2. I disagree. I feel the correct answer is D - not enough information is given. You make the assumption that the ball is thrown directly up. What if it is thrown by a major league center fielder to home plate. At it's highest point it's vertical velocity is zero, but it's actual velocity is not zero.

  3. It's interesting you say that. I had the same comment on edmodo. I agree that this point should probably be clearer. In class I actually throw a ball up in the air so the students know exactly what I mean. Combine this with the fact that the question is asked early in the year, before the introduction of vectors in either calculus or physics and confusion you suggest just didn't happen. But I agree. I should have said the the ball is thrown straight up in the problem to clarify. Thank for stopping by and adding your thoughts.

  4. Acceleration from the moment it leaves your hand is always -9.8 m/s2 if I'm not mistaken, and Velocity can be whatever but never less then 0. So I agree no matter what that the answer is B


    1. Hi Eric,
      You are correct about the value of acceleration, at least on this planet, but velocity can be negative. It is speed that must always be positive, a source of confusion for teachers and students alike. At the moment we are discussing in this problem, the velocity is zero while the acceleration is negative as you suggest.

      Thank you for stopping by with your comments.