Can we talk? About Isaac Newton and his laws of motion? Oh my. This is such a tough subject in elementary school.
First, students usually have very little knowledge of Newton. When you ask who he might be they immediately think of a famous football player named Cam Newton. (Mind you, we live in Alabama so Cam was a pretty big deal a few years ago.)
Second, the laws of motion are quite complex in their wording. Just reading the laws is confusing.
Third, hands-on will work best with younger students so how do you make these laws project-based?
I have some fabulous ideas for you!
So, let’s talk about the Laws of Motion – step-by-step!
For those of you that are interested in the non-kid-friendly versions here are the three laws.
- Law 1 – An object at rest will stay at rest and an object in motion will stay in motion on a straight path unless an unbalanced force acts upon the object.
- Law 2 – The acceleration of an object is dependent upon two variables- the net force acting upon an object and the mass of the object. The net force can only be determined if all the forces acting upon the object are known.
- Law 3 – For every action there is an equal and opposite reaction.
Now, I teach elementary students. These complicated scientific renderings have to be simplified! And a hands-on approach always walks best! #right
For students I try this explanation: If an object is not moving it will never move. If an object is moving it will continue to move in the same direction forever. After stating this I wait until students begin to question the thinking. When they start talking I demonstrate.
I place a ball on a table. It is at rest. It will stay at rest forever. Okay, they usually agree. Then one of them will say that it will move if I hit it. That is when I mention the rest of the law of motion. It will stay at rest unless an unbalanced force acts upon it. That would be the student hitting the ball.
Next, I roll the ball slowly across the floor while telling the students that the ball will keep rolling forever. Well, of course, it doesn’t! It bumps into a table or the wall and goes in a different direction or stops. I usually don’t even have to tell them that an unbalanced force has acted on the ball. They start saying it before I do!
The question then becomes- what is Newton talking about? Where can we prove this law? Outer space! An object moving in space has no friction, gravity, air resistance, or anything else to stop its forward straight path. It will continue to move unless it runs into something.
This is still hard to understand for some age groups! I found an amazing video that shows objects being tested in zero-gravity. I will link the video for you at the end of this post! When I show this video students have an ‘aha” moment!
Oh, goodness, this one has such complicated terminology. So, here is how I simplify it. The farther you want something to go, the harder you must throw or kick it. The heavier something is, the harder it is to move it.
Newton, of course, has a formula for this: force = mass x acceleration. The shortened form is F= m x a. This is not something I generally bring into the discussion. Remember, I am working with third, fourth, and fifth graders.
This law is, by far, the easiest to understand. I usually use a purchased Newton’s Cradle to teach the law. I demonstrate by pulling up one ball and dropping it and the students are fascinated when one ball swings from the other side and then repeats. Then I ask them what they think will happen if two balls are dropped. They almost always say that one ball will swing out the other side. There are always exclamations when two balls swing instead. I repeat with three and then four until they finally say, “Okay, equal and opposite reaction!”
Project for Law 2 – Marshmallow Blow Tubes
So, how can we use a project to show this law of motion? Here is the perfect one! In this multi-day activity, students use cardboard tubes to blow marshmallows and measure the distance traveled. The marshmallows are placed in the front of the tube or the back closest to their mouth. We use two lengths of cardboard tubes. A student (the designated MM blower) places the marshmallow at the far end of the tube and blows hard. The MM pops out and they measure how far it traveled. This is repeated 5 times and then they average the distances. Then they repeat the experiment but place the marshmallow at the other end of the tube. After trying this with the short tube the whole process is repeated with the longer tube. So, what do we hope to see?
Ideally, you want the measurements to show that the marshmallow traveled the farthest when blown from the spot closest to their face with the longer tube. An additional explanation of the second law of motion includes that the longer a force acts on an object the more acceleration it will have and the farther it will travel. So, the longer tube with the marshmallow at its far end keeps the marshmallow inside the tube for longer. The strength of the air blown should be greater for a longer time. The marshmallow should go farther.
Now, does this work? Yes, it works enough to prove the point of the experiment. Teams will get larger numbers with the longer tube. They will also have some results that vary widely. That is when we learn the term ‘human factor’. You cannot expect the strength of the blow each time will be the same. You must also consider the act of friction as the marshmallow travels through the tube. The results do vary. And this is a good time to discuss the scientific method and what scientists would do next. They would repeat the experiment or change one of the variables. Instead of cardboard tubes try a plastic pipe and see how the results compare.
Even though we see a wide range of answers this project still proves Newton’s Second Law and just think about all the other parts that were enriching- measuring, calculating averages, learning about variables, using the scientific method, and more! It’s a super activity.
NOTE: We cover the end of the blow tube with plastic wrap and blow through a hole in the wrap. This keeps the tube free of droplets that might spray when students blow into the tube. Also, one student is the team blower and no one else can use the tube. After class, I throw away the tubes.
Project for Law 2 – Egg Cars
In this challenge, students build a car that will hold an egg. The car is then rolled down a ramp with the goal of rolling the farthest distance without losing the egg. We try different angles of ramps to find the one that works best for each car.
There are many design elements in this project that must be considered. Students have to design an axle that will hold the wheels up and hold the weight of the car. The wheels also have to roll!
It is a challenging project, but my third graders always cheer when they see Egg Cars on their agenda. (I think it is seeing the word ‘egg’ that they are excited about!)
Before beginning this project we talk about the second law of motion. With this project, we can talk about outside/unbalanced forces that might act on the rolling object and alter its path. Friction and rolling into the side of the ramp is a concern. The weight of the egg is also a factor in how the car rolls.
According to Newton’s law, the higher ramp should make the car go farther since more acceleration will happen with that steeper incline. Even with the weight of the egg, the car should go a longer distance.
So, does this work? Yes, it does! For the well-made cars we did see the rolling on the steeper ramps making the car go faster and farther. Some cars didn’t travel well because of the car’s design rather than the ramp being too steep.
NOTE: There are some considerations that will cause problems that have nothing to do with Newton. We learned that the transition from the ramp to the floor was a definite factor in what happened to the car at the bottom of the ramp. With the steeper ramp that impact with the floor often caused the car to tip over or skid sideways. Many teams had to use the less steep ramp to make sure their car continued traveling when it reached the floor.
Again, what a fabulous learning experience this project was!
Projects for Law 3 – Balloon and Bottle Cars
I have three projects we use to try this law of motion in a hands-on way. The first two are both car challenges. Both cars are propelled by a released balloon.
In Balloon Cars, students have a paper plate, cardboard, and items to make the wheels and axles. They must also determine a way to attach the blown-up balloon. When the balloon is released the car will zoom forward.
The video below will share one of our most successful cars!
For Bottle Cars, we also use a balloon but we have different materials for the body for the car.
Students thread a straw through an empty water bottle to create a tube for blowing up the balloon. This one is very competitive- of course, they may be because I set up side by side tracks! Video below:
When we talk about both of these projects in regard to Newton’s Law, the students conclude that the two opposite actions are the balloon expelling air which makes the car roll in the opposite direction.
Project for Law 3 – Newton’s Cradles
My fifth graders build Newton’s Cradles! We take a look at the one I purchased and they are challenged to build a model!
They have craft sticks, strings, marbles, and straws or beads. This is one I only use with fifth grade because we use hot glue to hold the device together.