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This is the perfect summer activity for bored kids. My two oldest kids (ages 10 and 8) were bored and throwing balls around the house, so I grabbed a jar and one of their balls and gave them a STEM challenge. I asked them if they could pick up the ball with the jar. At first they stared at me blankly, but then I could see the wheels spinning in their heads and the excitement in their eyes. They were anxious to give it a try.
After a few unsuccessful and one successful attempt (which was different than what I was planning to show them – he used the edge of the table to pick up the ball!), I eventually taught them this STEM-based method.
We’re using centrifugal force and Newton’s First Law of Motion to move the ball into the jar by rotating it. It takes some patience and practice, but after a few tries it is a fun way to pick up the ball! My kids picked it up pretty quickly, but it took me at least 5 tries to pick up the ball! So do not give up if you don’t get it on your first try.
We did this without my toddler because she didn’t have the fine motor skills development and patience that is needed to make the circular motion to pick up the ball yet. She would have had a difficult time with the activity. My older two kids were the perfect age for this activity: they found it challenging but were both able to successfully complete the challenge.
Watch a Video of the Activity
I’ve created videos explaining the activity on both YouTube and Instagram. This is an activity where the videos demonstrate it a lot better than my photos and words can, so I highly recommend watching either the YouTube video embedded below or my Instagram reel linked after that for a video demonstration before you attempt on your own.
Watch the @engineering_emily Instagram reel below:
Activity Overview:
This is a simple, but difficult STEM challenge for older kids. This activity requires concentration and coordination to rotate a jar in a consistent circular motion that will allow you to pick up a ball with the jar. Don’t worry if you don’t get it on the first try, it takes practice and patience to get it right! I recommend this activity for children ages 5+.
Materials:
- Mason Jar
- Ball (we used a soft nerf golf ball, similar to the balls linked here, but any small soft ball will work)
Safety:
The jar is breakable because it is made of glass. Be careful not to bang the jar on a hard surface or drop it onto a hard floor to prevent it from accidentally chipping or shattering.
You will be moving the ball around in a circular motion inside the jar. If the jar is flipped too slowly the ball can go flying out of the jar in any direction. I recommend clearing a wide radius in your room of any breakable items, and using a soft ball to prevent injuries to people or breakage to items that could get accidentally hit with the ball.
Procedure:
- Place the ball and jar in front of the child.
- Ask the child if they can pick up the ball using only the jar (their hands can only touch the jar, not the ball).
- Let them brainstorm and experiment with ideas of how to pick up the ball. No wrong answerers: creativity and curiosity are encouraged at this stage!
- Eventually teach the child how to pick up the ball using centrifugal force if they don’t figure it out on their own by following the step 5 to 7 below:
- Place the jar top opening facing down over the ball on the table.
- Grab the side of the jar and begin to rotate it quickly in a clockwise direction, touching the ball with the jar as you rotate it. The ball will start to rotate with the jar and move up into the jar.
- When you see the ball move into the jar quickly flip the jar so the opening is facing upwards using a scooping motion, and the ball will be inside the jar! You picked it up.
- Repeat the activity testing different variables to see what makes it work better or worse:
- Rotate the jar clockwise until you catch the ball, then counterclockwise the next time you catch the ball. Did you get the same result?
- Rotate the jar slowly until you catch the ball, then quickly until you catch the ball. Which speed worked better?
- Wait as long as you can keep rotating it the jar before catching the ball, and then try catching the ball after just one rotation. Did length of time rotating the ball make a difference?
STEAM Concepts Learned:
This experiment works because of centrifugal force and Newton’s First Law of Motion. Centrifugal force is the effects of inertia that appears to push an object away from the center of a circle. Newton’s First Law of Motion states that an object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force.
When the rotating jar touches the ball, the ball begins to rotate in the same direction of the jar (due to Newton’s First Law). The ball is forced against the edge of the jar due to centrifugal force, and stays there as long as the jar keeps rotating in a steady motion.
This allows the ball to move into the jar and it will stay there as long as you keep rotating it. If you’re ready to stop rotating the jar, quickly flip the jar with a scooping motion so its opening is facing upward. The ball will be trapped inside the bottom of the jar.
My kids and I had lots of laughs as we tried to get this activity to work. It took us many tries to get it right, which can be frustrating. We initially started getting frustrated, but then started laughing as we tried swirling the ball around in the jar and flinging it around our room as we tried to catch it.
I was glad our ball was a soft nerf ball because it flew all around our dining room as we figured out how to do the scooping motion to collect the ball in the jar. It was silly and entertaining activity, whether we picked up the ball or not. My kids and I thought it was a great boredom buster. Let us know if you try the activity and if you have success!
