Have your kids ever wondered how big is a rain drop? Here is a really fun science experiment for older kids to use STEM to measure how big a raindrop is.
How big is a raindrop?
This science question is perfect for middle school students who should be stretching their algebraic muscles. With support advanced elementary students might enjoy engineering their own answer or high school students might find it an amusing math warm up.
Raindrop Science Experiment
To start this challenge, ask your child how big a rain drop is. Let them puzzle and guess for a while before giving them a method. It could be that they'll develop their own genius way to solve the problem!
If they seem stuck, give them their materials. Again, as a teacher, you don't want to give them a scrap of information more than they absolutely need.
Materials:
- Container for rain drops- the bucket off of out Learning Resources Balance was perfect
- Paper cut to the size of the top of the container
If they're still struggling, you can give in and tell them how to figure it out.
How to measure a rain drop
Place the container in the rain, note what time it was when you put the bucket outside.
Hold the paper under the rain for just a few seconds. Write down the number of seconds, and count the rain drops. If there are too many to count, divide the paper into sections count the number in one section and multiply by the number of sections to estimate how many rain drops are on the paper.
Now that you've told them how to do it, you can leave them to their work.
How to calculate the size of the raindrop
Of course, you want to be sure you know the answer to your own question, so here is the method I would use to calculate the size of the rain drop.
You know the number of drops that landed in the paper, and how long you held the paper in the rain. You can write this information as a ratio- n drops/x seconds.
You also know the volume of water in your container and how long it took to collect. Again, write the information as a ratio.-V volume/y minutes.
Use a unit multiplier to change minutes to seconds.
Multiply your first ratio by the same number (eg 120n drops/ 120x volume) until the number of seconds on the bottom equals the number of seconds in the second ratio. It's kind of saying that had you kept counting for as long as the volume collected, you would have gotten the bigger number.
Now you can say that that big number of drops equals the volume of water. To find the volume per single drop, divide the volume by the number of drops.
Extension ideas
To extend this lesson you could find an official size of a raindrop, calculate percentage error and write an explanation of error.
You could also do a painting with water soluble paint then briefly expose it to a rain shower. What volume of water sprinkled the painting?
Move on to the question, (How many veins are in this leaf?)
Christy McGuire is a former AP physics teacher, and current mother of 4. She and her children enjoy exploring science and math together. Head over to Thriving STEM to find more science, technology, engineering and math ideas to use with your kids. Follow along on Facebook, Instagram, Pinterest, and Twitter.
