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Unit: Laws of motion

This lesson reviews different types of forces and how to draw free body diagrams to represent the forces on an object.
Newton's third law says that forces always occur in pairs. For example, if the Earth is pulling down on you, you are also pulling up on the Earth with a force of equal magnitude and opposite direction.
A dog is balancing on one arm on my head. Is my head applying a force to the dog's hand? If it weren't, wouldn't there be nothing to offset the pull of gravity causing the acrobatic dog to fall? What would we call this force? Can we have a general term for the component of a contact force that acts perpendicular to the plane of contact? These are absolutely normal questions to ask.
You will often hear physics professors be careful to say "net force" or "unbalanced force" rather than just "force". Why? This tutorial explains why and might give you more intuition about Newton's laws in the process.
This short tutorial will have you dealing with orbiting frozen socks in order to understand whether you understand Newton's Laws. We also quiz you a bit during the videos just to make sure that you aren't daydreaming about what you would do with a frozen sock.
What forces are acting on you when you slide down a frictionless ramp? In this lesson we'll learn how to analyze the motion of an object on an inclined plane.
We've all slid down slides/snow-or-mud-covered-hills/railings at some point in our life (if not, you haven't really lived) and noticed that the smoother the surface the more we would accelerate (try to slide down a non-snow-or-mud-covered hill). This tutorial looks into this in some depth. We'll look at masses on inclined planes and think about static and kinetic friction.
Bad commute? Baby crying? Bills to pay? Looking to take a bath with some Calgon (do a search on YouTube for context) to ease your tension? This tutorial has nothing (actually little, not nothing) to do with that. So far, most of the forces we've been dealing with are forces of "pushing"--contact forces at the macro level because of atoms not wanting to get to close at the micro level. Now we'll deal with "pulling" force or tension (at a micro level this is the force of attraction between bonded atoms).
When two or more objects must move with the same magnitude of acceleration (like masses on strings, or boxes pushed into each other), we can treat the entire system as a single object when finding the acceleration.
In this lesson, we'll learn about momentum and how it is transferred. Whether you're playing pool (or "billiards") or deciding whether you want to get tackled by the 150 kg person, these concepts are of key importance.
Depending on your view of things, this may be the most violent of our tutorials. Things will crash and collide. We'll learn about momentum and how it is transferred. Whether you're playing pool (or "billiards") or deciding whether you want to get tackled by the 300lb. guy, this tutorial is of key importance.

About this unit

Let's learn about what a force is and how Newton changed the world's view of how reality works.