How to use water and gravity to twist a soda can

Summer is the best time for outdoor science experiments. We always seem to tackle harder science topics in the summer because the days are longer and the minds are sharper from all that extra time spent outside.

Twisting Soda Can experiment is a fun way to twist an empty soda can without touching with hands, but with the crafty use of the force of gravity. You can call it an Introduction to Physics for Little Kids.  

 

 

Twisting is one of the most common actions we perform daily. According to the Oxford dictionary, twisting means bending into a specified position, moving in such a way that two parts of a body are facing in opposite directions or causing to rotate. The subject of this post is the latter part of the definition causing things to rotate or twist.  

 

To make it a terrific learning experience start by asking some questions about twisting. What can you do to twist an empty can of soda without using your hands directly? Is it possible to twist a can of soda by filling it with water?  Why or why not? Would poking holes in a can help it twist? Does it matter where the holes are? Their shape?    

 

My family doesn’t buy or consume any products that come in cans, so we had quite an adventure looking for cans in recycling bins in back alleys. What we wouldn’t do for science! We found that longer cans twist much faster than standard cans, so if you can get hold of a beer can, that would work even better than a soda can.  

 

Twisting Soda Can Experiment for Kids

What you need

Empty soda (or beer) cans (3-4)

Nail for making holes

String

Water

 

Procedure

• Poke three holes in the bottom of a soda can. We used a nail and angled it to give water a direction.

 

• Tie a string or shoelace to the top of the can and fill it with water by submerging it in a pot of water (or use a garden hose to fill it up).

 

• Lift the can in the air by the string and watch it rotate. 

 

 

If you have observed my kids’ excitement in person, you would have thought they have never seen the water before.  

 

They wanted to do it again and again and again.  

 

Variations

Now vary the position of holes:  

• We did three holes along the top of the soda can.  
• Three holes horizontally, one on top of another, on one side of the soda can.  
• And a random collection of holes all over. 

None of the new varieties produced a spinning motion, but we had fun trying.  

 

The Science of Twisting

The position of holes and their direction are of the utmost importance. When we poke holes around the bottom edge of the can, we harness the power of the gravitational pull. The pressure of the water as it pours out, plus the angle of the holes makes the can spin. When the holes are positioned along the top edge of the can, the water is not coming out with force and, nothing exciting happens.  

 

Trouble Shooting

1.  If your can is not twisting, you might want to change a string. We had to try five different models before we found the best fit. 
2.  Keeping a can straight helps the rotation, so if your can is leaning glue the top flap (the one you pull up to open the can) to the can. This way when you hold it by the string, the can will be parallel to the ground. 
3. We found that larger and longer beer cans rotate much faster and in more impressive fashion than regular 11 oz soda cans.  

 

To better understand the basics of twisting, please, read this post The Physics of Twisting for Kids.