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Physics Question of the Week

Each week, we highlight one of our many demonstrations by asking a physics question relevant to the topic designed to be illustrated. This not only challenges audiences to carefully examine their previously held views on physics, but also provides suggestions for teachers looking to use these demonstrations in their own classrooms.

Be sure to check back each week for the solutions to the previous weeks' questions and for newest question of the week.

  • Question of the Week Archive
  • Question of the Week 4/14-4/18 with Answer
  • Question of the Week 4/07-4/11 with Answer
  • Question of the Week 3/31-4/04 with Answer
  • Question of the Week 3/24-3/28 with Answer

Shown in the photograph below are two aluminum tubes. They have the same length, but the tube on the right has a cap on one end. Physicists would say the the tube at the left is "open" and the tube at the right is "closed." If you click your mouse on the photograph below you will hear Gwen creating a musical tone by blowing across one end of the open tube.

h3-24

 

Now suppose that Gwen were to blow across the open end of the closed tube. How would you compare the frequencies of the tones of the tubes?

The frequency of the closed tube is:

  • (a) higher than that of the open tube.
  • (b) lower than that of the open tube.
  • (c) the same as that of the open tube.

Now suppose that Gwen were to blow across the open end of the closed tube. How would you compare the frequencies of the tones of the tubes?

After April 18th, 2014, click Read More for the Answer

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Shown in the photograph below is a small fuse box as seen through a magnifying glass.

 l6-12

Now suppose that the entire magnifying glass and fuse box assembly were placed into the tank of water seen at the rear of the picture behind the assembly.

After the magnifying glass/fuse box assembly is placed into the water the letters on the fuse box will appear:

  • (a) larger.
  • (b) smaller.
  • (c) the same size.

After April 11th, 2014, click Read More for the Answer

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A long thin rod is held vertically on an air table. An air puck provides for sliding without friction of the bottom end of the rod when the rod is released. A small weight equal to the weight of the air puck attached to the top end of the rod makes the rod symmetric, equivalent to a thin uniform rod.

 c1-21

The question involves what the rod does when the top end is released and it is allowed to topple. In particular, will it topple like a falling chimney, so that the bottom end of the rod remains at the same point? Or will the bottom end begin to slide when it is released - after all, the bottom end slides without friction on the air table - so that the top end will fall straight down to the point where the bottom end was when it was released? Or perhaps the center of mass will move straight downward. What is the important physics concept that governs how the rod will topple?

When the rod is released, it will fall with

  • (a) the bottom end remaining at the same point.
  • (b) the top end moving straight down.
  • (c) the center of mass moving straight down.

After April 4th, 2014 click Read More for the answer

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Two square balls are mounted as shown on the apparatus pictured below.   When the system is tripped the ball at the left is released from rest and falls downward; ball at the right is projected horizontally and falls to the floor in a parabolic arc.

c2-21 c2-21a 

The question for this week involves how fast the two balls will fall to the floor.  In particular, after one is released and the other projected horizontally, which ball will win the race to the floor: the falling ball, the projected ball, or will the race end in a tie.  The falling ball might get to the floor first because it will travel a shorter distance.  On the other hand, the projected ball might get to the floor first because it starts with more kinetic energy, and it will therefore go faster.

When the apparatus is tripped, sending the balls on their respective paths to the floor:

  • (a) the ball released from rest will arrive at the floor first.
  • (b) the ball projected horizontally will get to the floor first.
  • (c) the two balls will get to the floor simultaneously.

After March 28, 2014, click Read More for the answer.

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