Two Cupcake Cups Coming Together in the Air

Let's take a look!

Watch the video on YouTube.

What type of experiment is this?

Experimental procedure and explanation:

• Take two cupcake cups and drop them from slightly different heights.
• The two cupcake cups come together partway down, and then proceed to fall together.
• When the two cupcake cups are initially separated, the pressure on the top cup decreases because the air resistance acting on the top cup is smaller than the air resistance on the bottom one. The top cup therefore falls faster than the bottom one, and eventually the top one catches up with the bottom one. An alternative explanation for this is that the lower cupcake cup obstructs the air and reduces the air resistance on the top cupcake cup.
• If the top cupcake cup moves to the left or right, flow from below hits the protruding part, and force acts on the cupcake cup to return it to the center. This force keeps the two cupcake cups in line with each other. However, this experiment will not work if the vertical gap between the two cupcake cups is too large.

[Keywords]	Air resistance, Terminal velocity
[Related items]	Slowly Falling Cupcake Cup, Gaining a Benefit Behind a Large Object
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, P136－139. “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, P66－69.