Summer can be a welcome break from formal lessons, but that doesn’t mean it has to be a break from learning. A collection of toys that are probably already in your beach bag is all you need to turn the pool . . . or a storage tub full of water . . . into a floating summer science lab. Check out these five simple science activities and brush up a little on your own science knowledge to help your children understand science without even having to think about school!
Exploring Bernouilli’s Principle at the Pool
OK, who of us hasn’t stuck their hand out the window to feel the force of the wind rushing past? Young children are natural explorers and will discover quickly how to make their hand dive and rise again just by tilting their hand in the wind. Connecting that to how an airplane’s flaps works is pretty easy and if your child has actually seen the flaps on an airplane’s wings, he or she may make the connection immediately.
Why does it work?
It’s all about Bernoulli’s Principle. OK, so for you physics people, there is a whole lot more to it than that, but for your children who are still young enough to pretend to be an airplane on the way to the pool, Bernoulli is enough.
Bernoulli’s principle states that the increase in the speed of a fluid (and yes, air is a fluid ←That link takes you to another simple experiment to demonstrate) occurs simultaneously with a decrease in pressure. An airplane’s wing is flat on the bottom and curved on top. Since the air has to get to the back of the wing at the same time, whether it goes over or under the wing, the air traveling over the top goes faster. This faster air creates a low pressure area which helps give the airplane lift.
Of course, with your hand plane, you are feeling the force of drag, the wind pushing against an object, more than the lift caused by the changes in air pressure. But there’s no better time for discussing the principles of flight than while pretending to be an airplane! Go ahead and throw in how the car’s engine is providing thrust and how the weight of your hand determines how much thrust is necessary and you’ve discussed all four forces involved in flight!
Exploring Drag With Your Child
Drag is the force that acts opposite to the direction of motion. Thrust pushes you forward while drag literally sucks you backward. It is much easier to feel in the water because more pressure is involved. You can feel the effects of drag even as you just try to walk through the water because humans are not very hydrodynamic.
Find some aerodynamic (hydrodynamic?) toys. Those weighted bombs are perfect for this. Race them under water. Feel how smooth they move through the water. Then find (or make) a small parachute. How does it feel as you pull it through the water? What you are feeling is drag. For smooth motion, the surface of an object has to be smooth to “cut” through the water. The shape of the tail area is important as well. If you look at several objects designed to be aerodynamic, you will likely notice that they have the same basic shape. Take a close look at a submarine, an airplane and a shark. What basic shapes to they have in common? And when you look at their tail area, what do you notice?
Why are they shaped similarly?
Water and air are both fluid (see above). The same laws apply to both, however the drag is much easier to feel in water because the pressure is greater. As water (or air) flows over your toy, it looks something like this:
See that space at the back, before the arrows join? That’s a low pressure area, creating a vacuum at the back of your toy. It “sucks” at the back, slowing it down (and decreasing fuel efficiency). This is the drag we have been talking about. The tail area of anything made to be aerodynamic (or hydrodyamic) is designed to minimize drag while maintaining balance. The fins help keep the machine upright, but they also increase drag. The tail area is tapered to decrease drag, but tapered too much and it can be hard to keep the machine from simply spinning in the water. Mathematicians and engineers work out the perfect balance for decreasing drag while maintaining balance and then build models to test in wind (and water) tunnels to see if their theories worked. Try turning the pool into your own test lab with a variety of differently shaped toys. If you have an older toy, it could be interesting to carefully cut the fins off and see what happens when it moves through the water.
Exploring Buoyancy With Your Child
“Float and Sink” is kind of a staple science center in early elementary classrooms. Children are born scientists, always questioning and always testing. What can be more fun than gathering all your favorite (water safe) things to throw in the water?
Even young babies seem to delight in just dropping things in the water to see what will happen. Older children can begin sorting objects by whether or not they float. Which of the floating toys could carry the sinking toys across the pool?
Once they are old enough to begin to make predictions about which objects will float and which will sink, they are old enough to begin to understand buoyancy. Gather several items and have your child predict which will float. Most important, ask why. She may think the dive ring sinks while the bottle floats because it is heavier, but why does a huge cruise ship float? Can you find items in your collection that float even though they are heavier than the sinking ones? Can any of them float while carrying one of the sinking toys?
Why does it work?
Archimede’s Principle states that the upward force (buoyancy) of a fluid (in this case water) is equal to the amount of water displaced by the object. So if you have a 10,000 pound ship, it has to displace over 10,000 pounds of water to stay afloat. That’s why a ship stays afloat unless something cracks the hull and it begins taking on water. Once enough of the ship is filled with water, it no longer is displacing enough water to stay afloat and it begins to sink.
Can you find anything with neutral buoyancy?
This is easier to demonstrate in a sink or pitcher, but you can actually measure the amount of water something displaces. Mark the edge of water and see how much it rises when you place something in it. What happens if you take an empty container and force it mostly below the water? And as you let the water rush in?
To really demonstrate the principle, try making this simple (if you know a little origami, anyway) paper boat and then recording how many pennies it holds before sinking.
And if you want to take a look at how buoyancy and Bernoulli’s law work together to make a submarine surface and dive, check out this short video on how submarines work!
Exploring Air Pressure With Your Child
For this, you need squirt guns. Or seahorses, dolphins or even soap bottles if you don’t like toy guns!
Water fights on a hot day are always fun, and some of the newer squirt toys for the pool can shoot whole columns of water quite a distance! Have you ever wondered why the water doesn’t just come pouring out of the hole, even when you aren’t squirting it? OK, so you may know, but have you explained it to your children?
Start out by getting your children curious. Hold several different squirt toys upside down. Some may dribble, but unless there is a hole somewhere, they really shouldn’t drain out. What happens if you open the stopper? If you poke a nail hole into the soap bottle? How about if you fill a milk jug and just turn it upside down without a lid?
There are actually two things going on to keep the water in.
First, nature abhors a vacuum. For water to come out, it has to be replaced by something. If the hole in the dispenser end is big enough, air will go up through the liquid while the liquid is coming out. That’s why milk jugs and soda bottles “glug” if you dump them by turning them upside down.
Second, air exerts pressure. 14.7 pounds per square inch at sea level, to be exact. In the case of your squirt gun, the air is exerting more pressure on the water than the water is on the air, so the air actually holds the water in the gun.
Once you squeeze the trigger, the pressure increases enough to send the water shooting out.
Really want to impress your kids? Try some water glass magic. Fill a glass of water to the top and place a note card over the top. Flip it quickly and watch as the air pressure holds the note card against the opening, holding all the water in!
Exploring Volume With Your Child
Assemble a variety of toys for filling and dumping. Don’t forget a set of measuring cups. These are great for teaching young children about volume and measurement. How many quarter cups does it take to fill a cup? How many cups fill a pail?
To really challenge their concept of volume, take several different sized containers and put the same amount of water in each one. Especially young children have a tendency to see height more than width, so they will think a tall thin container has more water in it than a short fat one. Help them to see that they contain the same amount of water by pouring the water back and forth between the different containers and the measuring cup.
If you have a set of geometric solids, try filling them up with water and comparing their volumes as well!
Are there are any other must-have toys or games you take with you to the pool to squeeze a little learning into the fun? If so, please share!