1. Chapter 4 Newton’s 1 st Law Aristotle – Believed that in order for an object to move, a force had to be pushing it. “All objects have a natural state of rest. Heavy things have a natural state on The ground, and very light things have A natural state in the air, such as smoke.”

2. Galileo Galilee Galileo’s experiments: A)Yes B)No Assume the ball- floor friction is negligible Which of these images are or are not accurate

3. Galileo’s ideas Through his experiments, objects in motion want to stay in motion, the reason objects come to rest is because of friction. Friction is the force that opposes motion. Friction put a wrench in his calculations on motion – he needed a new form of math – Calculus Coincidentally, Galileo’s views on motion were taken with a lot of criticism. Aristotle’s views had been accepted for 2000 years – how could Galileo be “smarter” than Aristotle???

4. How would Aristotle view a ball rolling across the table and slowly coming to a stop? A) Friction makes the ball stop B) The ball wants to come to its “natural” resting state C) Gravity makes the ball stop How would Galileo say the ball stopped?

5. How does friction work? Friction from the microscopic level: The force that opposes motion in the opposite direction is called friction When objects are in contact with each other, microscopic ridges and valleys create the “resistance” to motion. Smooth objects have less contact points than rough objects.

6. Discuss these in your group How could you get reduce the time it takes you to go down a waterslide? Why are socks more slippery on the floor than bare feet? Why is rubber used for tires instead of other cheaper materials (plastic)?

7. Newton’s 1 st Law At age 24, Isaac Newton came up with his world changing 3 laws of motion. The first: An object continues in a state of rest or in a state of motion at a constant speed along a straight line, unless compelled to change that state by a net force i.e. An object in motion stays in motion and an object as rest stays at rest unless changed by an outside force.

8. Concept Quiz If the force of gravity between the planets and the sun were to suddenly disappear, what path would they follow? If the force of gravity between the planets and the sun were to suddenly disappear, what path would they follow? A B C D

9. Inertia Mass – A measure of matter (stuff) that makes up an object. Inertia – an objects resistance to change, which is related to mass (it’s harder to move a train than it is a car). The inertia of an object IS measured by its MASS. Newton’s 1 st law is sometimes referred to the law of inertia. A measure of inertia = mass Which has the most inertia? A) An empty canB) Can full of water C) Can full of sandD) Can full of a vacuum

10. Will it be just as difficult to shake a bowling ball in space as it is on earth? A) Yes B) No Will it be just as easy to “wind up” a bowling ball in space? Does a 2 kg bunch of bananas have 2 times as much inertia as a 1 kg block of steel? Does a person have less inertia on the moon?

11. Mass vs Weight Mass is different than weight Mass is the measure of matter in an object (the number and type of atoms). This is measured with a balance.

12. Concept Quiz Will you have the same mass on the moon? A) Yes B) No SI unit for Inertia and Mass: Kilogram (kg)

13. Weight Weight is the force of gravity on an object. It is measured with spring scales. A scale will compress due to gravity. Weight IS a FORCE.

14. Weight Weight is a force! It is measured by taking the mass of an object multiplied by gravity (and gravity can change!). Weight/Force (N) = mass (kg) x gravity (m/s²) The SI unit for weight is the Newton. (One Newton is equal to about a ¼ burger)

15. Concept Quiz At the doctor’s office, a balance measures the future Mr. Shaffer to be 255 lbs of pure solid muscle. What is his weight? (2.2 lbs = 1 kg) A) 116 kg B) 255 lbs C) 255 kg D) 1137 N E) 2499 N

16. Net Force The combination of all forces acting on an object

17. Equilibrium When the net forces equal zero. There is no acceleration.