Have you been soaked in a little April shower lately?  Pesky aren’t they? It’s time for the new Planet Science Quiz and this time it’s the April Aquifer Quiz It’s all about water and if you get all the answers right then you go into the hat for a one of three water battery powered clocks! Surely that can’t be right? Powered by water? Strange but true.

Free-falling water

This can be messy so best do it outside! 

You will need:

• a disposable polystyrene cup
• something to make a hole in the plastic cup with
• water
• an outdoor area, ideally over a garden or some grass
• a bucket

What to do:

1. Make a hole in the side of the cup, near the bottom.
2. Hold the cup so your thumb covers the hole.
3. Fill the cup with water.
4. Hold the cup up as high as you can.
5. Uncover the hole. The water will squirt out in a steady stream. Try not to aim it at anyone, unless they have annoyed you.
6. Try to predict what will happen if you let go of the cup. As the cup falls, will the water squirt out more quickly, more slowly or at the same rate?
7. Let go of the cup. What happens? The water stops flowing out almost instantly!

What’s going on?

When you were holding the cup, gravity was pulling down on the cup and the water. The cup didn't move, because you were holding it. Gravity also pushes the water down against the bottom of the cup. The water at the bottom of the cup squirts out because of the weight of the water above it pushing it against the bottom of the cup.

When you let go of the cup, gravity accelerates the cup and the water inside it equally, so they fall at the same speed. Since they are falling together, the water doesn't feel a force pushing it against the cup any more, so the water doesn't squirt out.

The same thing happens inside a spacecraft. When an astronaut is sitting inside a spacecraft on the ground, gravity pushes them down into their seat. Once the spacecraft has launched and the engine is turned off, the only force acting on it is gravity. The astronaut appears to be weightless because gravity accelerates the astronaut and the spacecraft equally, just like the water and the cup. The astronaut doesn't feel any force pushing them against the seat, just like the water didn't feel a force pushing it against the cup.

A better term for the way things in spacecraft seem to be weightless is "free fall", because both the spacecraft and the astronaut are falling without anything stopping them.

This activity was taken from Science by Email

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