Newton’s First Law

So, what’s next? We’ve learned how things move (speed and acceleration) in a 1 and 2-dimensional plane Now, we’ll learn what makes them move. What causes things to move? What is force? How do you measure force?

Let’s learn from a toy car Hypothesize what will happen when: The toy car is not pushed The toy car is pushed The toy car is pulled with a rubber band (Remember to use the word force & motion in your hypotheses) Experiment Results Conclusion—explain what you saw. What had to happen for the car to move? Push on it or Pull on it

Newton’s First Law The law states: A force is a push or a pull Newton’s First Law is also known as the Law of Inertia The law states: “A body at rest, tends to stay at rest; a body in motion tends to stay in motion, until an external force is applied.” A force is a push or a pull It is a vector --> care about direction An external force means an outside force is being put on the object Examples: pushing against a wall pulling a sled A headwind against an airplane

To simplify it… A body at rest… (not moving) will continue not moving A body in motion (moving) will continue moving

Who is this Newton guy anyway? Isaac Newton was born on Christmas day of 1642 (died in 1727) He was the Einstein of the 1600s. At 24 years old, Newton developed his famous laws of motion, replacing 2000 years of thought. He also discovered gravity You will know his name so well 

Equilibrium Objects move only if the net force is not zero. The sum of all forces acting on an object is called the net force. When all the forces on an object balance out, the object is in equilibrium. When an object is in equilibrium it means it will stay at a constant velocity This is why it’s important to draw a picture! So we can figure out what the net force is (forces are vectors so direction is important!) These drawings are called free-body diagrams.

What is the net force on a book with 30 N of gravity pulling it down and 10 N of air resistance pushing it up?

If only… Many physics concept and laws we learn assume an ideal world. But sadly, we don’t live in an ideal world because there are other things at work. Newton’s First Law says an object in motion will continue in motion unless another force acts on it, many times in real life that force is known as friction Friction is a force that stops an object from moving In physics, we are going to pretend we’re in an ideal world and that there is no such thing as friction

Inertia  Eureka! video More mass more inertia! Inertia is an object’s “laziness” or resistance to change in motion Inertia is determined by an object’s mass Mass is the amount of stuff in an object and measured in grams, kilograms and milligrams Mass is not weight More mass more inertia! More inertia more force to change motion!

Newton’s First Law – Old School…

Now for the demos!!