Getting Started

We’re going to study velocity, acceleration, forces, and Newton’s three laws of motion in this section. You’ll get to throw things, build g-force accelerometers, and much more as you uncover the basis of all physics in our crash-course in projectile motion. Newton has a famous quote that goes “If I have seen farther then others, it is because I have stood on the shoulders of giants.” One of the giants he was referring to was Galileo. Thanks to the discoveries of Galileo and others, Newton was able to make many of his own discoveries. The most famous of which are Newton’s Laws of Motion.

Newton’s Laws are all they used to get the first man to the moon. They are an amazingly powerful and wonderful area of physics. I like them because evidence of them is everywhere. If something moves or can be moved, it follows Newton’s Laws. You can’t sit in a car, walk down the road, drink a glass of milk, or kick a ball without using Newton’s Laws. I also like them because they are relatively easy to understand and yet open up worlds of answers and questions. They are truly a foundation for understanding the world around you.

Here are the scientific concepts:

  • The motion of objects can be observed and measured.
  • The position of an object can be described by locating it relative to another object or the background.
  • An object’s motion can be described by recording the change in its position over time.
  • The way to change how something is moving is to give it a push or a pull. The size of the change is related to the strength, or the amount of “force,” of the push or pull.
  • Tools and machines are used to apply pushes and pulls (forces) to make things move.
  • Objects near the Earth fall to the ground unless something holds them up.
  • Each force acts on one particular object and has both a strength and a direction.
  • An object at rest usually has multiple forces on it, but they add up to give a net force sum of zero. Forces that don’t sum to zero are imbalanced, and cause an object to change speed or direction of motion (or both).
  • The patterns of an object’s motion can be observed and measured, and also predicted.
  • Objects exert forces on each other.
  • Electric and magnetic forces between a pair of objects do not require the objects be in contact. The size of the forces depend on the properties of the objects, their distance apart, and in the case of magnets, their orientation.

By the end of the labs in this unit, students will be able to:

  • Design and build an experiment that shows how forces are balanced and unbalanced, and how unbalanced forces cause motion in an object.
  • Make observations and measurements on an objects motion to figure out the predictable pattern of motion.
  • Figure out the electric and magnetic relationship interactions between two objects.
  • Differentiate observation from inference (interpretation) and know scientists’ explanations come partly from what they observe and partly from how they interpret their observations.
  • Measure and estimate the weight, length and volume of objects.
  • Follow a set of written instructions for a scientific investigation.

Select a Lesson

Special Science Teleclass: Physics of Motion
This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too! We’re going to cover energy and motion by building roller coasters and catapults! Kids build a working catapult while they learn about the physics …Continue reading”Special Science Teleclass: Physics of Motion”
Special Science Teleclass: Rocketry & Spaceflight
This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too! Blast your imagination with this super-popular class on rocketry! Kids learn about fin design, hybrid and solid-state rocketry, and how rockets make it into …Continue reading”Special Science Teleclass: Rocketry & Spaceflight”
Balloon Racers
We’re going to experiment with Newton’s Third law by blowing up balloons and letting them rocket, race, and zoom all over the place. When you first blow up a balloon, you’re pressurizing the inside of the balloon by adding more air (from your lungs) into the balloon. Because the balloon is made of stretchy rubber …Continue reading”Balloon Racers”
Look Out Below!
If you jump out of an airplane, how fast would you fall? What’s the greatest speed you would reach? Let’s practice figuring it out without jumping out of a plane. This experiment will help you get the concept of velocity by allowing you to measure the rate of fall of several objects. It’s also a …Continue reading”Look Out Below!”
Detecting the Electric Field
You are actually fairly familiar with electric fields too, but you may not know it. Have you ever rubbed your feet against the floor and then shocked your brother or sister? Have you ever zipped down a plastic slide and noticed that your hair is sticking straight up when you get to the bottom? Both …Continue reading”Detecting the Electric Field”
Newton’s First Law of Motion
First Law of Motion: Objects in motion tend to stay in motion unless acted upon by an external force. Force is a push or a pull, like pulling a wagon or pushing a car. Gravity is a force that attracts things to one another. Gravity accelerates all things equally. Which means all things speed up …Continue reading”Newton’s First Law of Motion”
Newton’s Second Law of Motion
Second Law of Motion: Momentum is conserved. Momentum can be defined as mass in motion. Something must be moving to have momentum. Momentum is how hard it is to get something to stop or to change directions. A moving train has a whole lot of momentum. A moving ping pong ball does not. You can …Continue reading”Newton’s Second Law of Motion”
Newton’s Third Law of Motion
Third Law of Motion: For every action, there is an equal and opposite reaction. Force is a push or a pull, like pulling a wagon or pushing a car. Gravity is a force that attracts things to one another. Weight is a measure of how much gravity is pulling on an object. Gravity accelerates all …Continue reading”Newton’s Third Law of Motion”
Barrel Roof
This roof can support over 400 times its own weight, and you don’t need tape! One of the great things about net forces is that although the objects can be under tremendous force, nothing moves! For every push, there’s an equal and opposite pull (or set of pulls) that cancel each other out. This barrel …Continue reading”Barrel Roof”
Building Bridges
What keeps building from toppling over in the wind? Why are some earthquake-proof and others not? We’re going to look at how engineers design buildings and bridges while making our own. Here’s what you need:
A Weighty Issue
This lesson may give you a sinking sensation but don’t worry about it. It’s only because we’re talking about gravity. You can’t go anywhere without gravity. Even though we deal with gravity on a constant basis, there are several misconceptions about it. Let’s get to an experiment right away and I’ll show you what I …Continue reading”A Weighty Issue”
Forever Falling
If I toss a ball horizontally at the exact same instant that I drop another one from my other hand, which one reaches the ground first? For this experiment, you need:
Rocket Ball Launcher
This is a satisfyingly simple activity with surprising results. Take a tennis ball and place it on top of a basketball… then release both at the same time. Instant ball launcher! You’ll find the top ball rockets off skyward while the lower ball hit the floor flat (without bouncing much, if at all). Now why …Continue reading”Rocket Ball Launcher”
Detecting the Magnetic Field
Remember, there are four different kinds of forces: strong nuclear force, electromagnetism, weak nuclear force, and gravity. There are also four basic force fields that you come into contact with all the time. They are the gravitational field, the electric field, the magnetic field, and the electromagnetic field. Notice that those four force fields really …Continue reading”Detecting the Magnetic Field”
Flying Paper Clip
Have you ever been close to something that smells bad? Have you noticed that the farther you get from that something, the less it smells, and the closer you get, the more it smells? Well forces sort of work in the same way. Forces behave according to a fancy law called the inverse-square law. To …Continue reading”Flying Paper Clip”
Force-full Cereal
Did you know that your cereal may be magnetic? Depending on the brand of cereal you enjoy in the morning, you’ll be able to see the magnetic effects right in your bowl. You don’t have to eat this experiment when you’re done, but you may if you want to (this is one of the ONLY …Continue reading