Here's a Question! - Finger in a Cup
A cup of water is placed on a digital scale. Steve puts his finger in the water without touching the cup. What happens to the reading displayed on the scale?
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: Here's a question for you...
A cup of water is placed on a digital scale.
Steve: What happens if I put my finger in the water without touching the cup?
Does the reading stay the same?
Joanna: Does the reading decrease?
Steve: Does the reading increase?
Joanna: Or is Steve electrocuted by the scale?
Pause the video now if you'd like to think it over before we show you what happens.
Steve: Placing my finger in the cup displaces some of the water. This creates a buoyant force that pushes up on my finger.
Joanna: For every action, there's an equal and opposite reaction. If the water pushes up on Steve's finger, then Steve's finger pushes down on the water.
Steve: This downward force is ultimately transmitted to the scale. The scale is squished by an additional amount, which causes the reading to increase.
Joanna: Thanks for watching. I hope you'll join us again soon for another question!
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