The force of water
Hold in your hands two plastic cups, one of which is full of water.
Step 2: Demonstrate to your audience that these are ordinary cups by pouring water from one into the other.
Step 3: And then back to the first cup.
Step 4: Repeat.
Step 5: Next, hold the cup with water over the empty one. And suddenly the water flows through the bottom into the cup below!
Step 6: How can that have happened? After all, the cup was completely whole!
Step 7: Take one more look.
The secret to the magic trick is that one of the cups isn’t as ordinary as it seems. It is made of two cups: one which has had the bottom cut out, and another which has had the top part removed.
Step 9: Fit the two cup pieces together. Hold the assembled cup together carefully while you pour the water back and forth. Then, holding the trick cup full of water over the empty cup, release the bottom and hold lightly onto the upper cup. The bottom of the cup falls together with the water into the cup below, completely unnoticed! Practice several times before performing this trick.