Projectiles: What Goes Up…

In my STEM enrichment class for kids (age 3 – 7), for the last class of the year, we go outside into the park and explore the physics of projectiles – learning about force and about gravity while having tons of fun throwing balls, shooting arrows, and launching rockets. It also links back to our very first class of the year – when we learn about “what is an engineer” and we challenge kids to find a way to launch a pompom.

The Science

It’s going to be ten years or so before any of these kids encounter this science in a high school physics class. But if they learn the basics of it now and experience it hands-on early on, then on that day in class, instead of being puzzled, they may get that a-ha of recognition and understanding.

So, here are some ideas and vocabulary you can introduce. In class, we talk about them at circle time, but if you’re playing one on one with a child, you don’t teach them in a pedantic lecture style: “and here is important scientific theory you must learn”. You introduce them as you play together: “did you notice that? do you want to hear something super cool about how the world works?” The goal is primarily playing together, secondary is encouraging them to notice scientific phenomena as a consistent pattern in how the world works, and the vocabulary is really just icing on the cake.

Force. The simplest way to describe force is that when you push on something, it moves, like this illustration of pushing a ball along a flat surface. forceIn my post on Force – Science for Kindergartners, I include all the Next Generation Science Standards related to this, but some other ideas to share about force is that it can have different directions (push or pull), when you push or pull you can change the direction or speed that an object is moving at, and (in general) the harder you push, the faster and further something will travel. It will keep traveling in that same direction till something stops it. (It has inertia.)

gravityGravity is an invisible force, that is pushing everything on earth toward the center of the earth. Kids already all understand how gravity works. (They know if you drop a ball, it will fall till it hits the ground.) You’re just giving them a word to describe their life experience. (Here are some gravity experiments for kids.)

Projectile Force is when an object is thrown, kicked, fired, or launched into the air. up down

Once you stop exerting the force (like when the ball leaves your hand), the object’s momentum keeps carrying it for a while, but gravity is pressing down on it, and eventually gravity will push it to the ground.

If you launch something straight up, it will come straight down. (Have your child practice this with a soft ball!)

trajectoryIf you throw something up and out, it will move up and away from you, then begin arcing down to the ground. This path is called its ballistic trajectory. I want the kids to notice that the path is a curve. (Technically the term is parabola.) Understanding this will be a great help to them in baseball, basketball, and any other arena where they’re trying to launch a projectile at a target.

The amount of time between the launch and the landing is the time of flight.

The Play

The joy of physics experiments is that many can be done anywhere, anytime with no specialized equipment.

Pick any object in reach – throw it and observe what happens – you just conducted an experiment!

Start your child’s day by tossing their clothes at them from across the room. Challenge them to toss their pajamas into the laundry basket. Poof! You’ve done science.

Here are some other key activities for exploring projectiles. (I link to some fun products that we’ve enjoyed playing with. FYI: Some include Amazon affiliate links – if you click on them and choose to buy something on Amazon, I get a small referral fee.)

Throwing, Kicking, Hitting Balls: You could play basketball, baseball, tennis, badminton, pingpong, soccer, kickball, etc.

Classic Kid Activities: You can shoot rubber bands. Or play with slingshots. Or throw darts. (I like magnetic darts.) Or throw water balloons. Or have an egg toss.

Planes and Rockets: Making and flying paper airplanes is always fun, and it’s easy to see the curve of the trajectory because they travel slower than some other projectiles.

Stomp rockets are really fun, and easy for kids ages 3 and up to use, and ages 4 and up can use independently. My favorite set is the stunt planes, because when you launch them, they glide to the ground. Always make sure to use them in a wide open space, or you WILL lose some to the trees. I also recommend buying extra rockets.

Estes model rockets are a classic parent-child science activity. (My family launched MANY rockets in my childhood!) They’re definitely parental supervision required.

Water bottle rocket launchers are also super fun. You fill a 2 liter bottle with water, pump it up, and launch it – 100 feet in the air! This is the model that we have and we’re pretty happy with it but you do want to make sure it’s on flat ground for the best launch. The same company offers DIY versions. You can also find instructions online for making your own.

Archery: You could certainly shoot real arrows if there’s an archery range near you. I also really like nerf archery. We bought a great set of Nerf crossbows 20 or 25 years ago that we still have. I like them because they have big soft arrows (very similar to a stomp rocket.) So, you can have battles where kids run around and shoot them at each other. We set the rule of no aiming at faces, but if they do accidentally hit someone in the face it doesn’t hurt.

I have not tried the newer Nerf crossbows – this one uses arrows, but comes with only 2 arrows so be sure to buy extras! This one uses crossbow bolts – little darts. If these are like the bullets for nerf guns, they can definitely sting if they hit bare skin at close range.

Nerf Guns: There are lots of different kinds of nerf guns. It is tons of fun for kids to run around shooting each other with Nerf darts. (You need to set limits on “no aiming at the face” and no shooting at close range, but it can be lots of fun.) But, I also get that toy guns can bring up complicated feelings at any time. I’ve written an article with my reflections on weapon play for kids and options to consider. Generally, I can see Nerf guns as fun, but in the current political and social climate, that would be harder for me to feel comfortable with. You could also consider allowing target shooting vs. shooting at other kids – the nice thing about nerf darts is that they fly with a pretty predictable amount of force/speed, so it’s a good way for kids to explore aiming at a target, and learn how they have to adjust for the trajectory. (Or, if you prefer, you could use slingshots or darts to aim at a target like knocking over a tower of plastic cups.)

Build a Launcher

There are lots of fun craft projects that allow you to create things that will launch objects into the air. Elsewhere on this blog (and my other blog), you’ll find instructions for how to build: catapults, alka-seltzer rockets (aka fizzy rockets), pompom poppers and puffers and a PVC slingshot.

Here are my instructions for building straw gliders and straw rockets.

I was super curious about this product, and I built one from a cardboard pizza box and a shoe box.

We’ve collected more fun ideas on our Pinterest page.

What’s your favorite thing to launch through the air?

Books? Songs?

OK, if you know of any good kids’ books about projectiles (fiction or non-fiction), let me know! For this class, I typically read The Girl Who Never Made Mistakes. It includes juggling, which is a projectile skill, but also has a great message about not having to be perfect – being OK with making mistakes and trying again.

I didn’t find a song about projectiles, and here’s the best one I could write, but it’s to the tune of Spinning Wheel by Blood, Sweat and Tears, so not exactly a familiar kids’ tune.

What goes up must come down
Gravity pulls to the ground
Launch it way up high, into the sky,
Do some physics testing, let gravity win.

You shoot the arrow up. It comes back down
Balls return to the ground
Testing out projectiles and you, you really learn
Do some physics testing, let gravity win.

If you know of something better (there’s gotta be something better), let me know.

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