1. M 9:30 - 10:30 AMCR 138 M 12:00 - 1:00 PMCR 136 W 12:00 - 1:00 PMCR 136 W 1:15 - 2:15 PMCR 138 F 12:00 - 1:00 PMCR 136 SI

2. Observe and Represent Forces Any push or pull, any interaction of objects Force is a vector!!! F [F] = N (Newton) How to measure forces?

3. Represent: Free Body Diagram Label each force arrow with an that has two subscripts. The first subscript is for the object that exerts a force on the object of interest, and the second subscript is for the object of interest. Represent an object with a dot (a point particle) and use an arrow to represent each interaction of another object with the object of interest. The tail of the arrow is on the dot. Pay attention to the lengths of the arrows on each free-body diagram.

4. Pick up a notebook and hold it stationary in your hand. Then pick up a textbook and hold it the same way. Do you feel any difference? For each situation (notebook and textbook) draw the free-body diagram. Forces Notebook Textbook Free-body diagram

5. The textbook is now on the inclined board. Draw a free body diagram for the book Textbook Normal force is always perpendicular to the surface W N θ

6. Net Force 5N 10N 5N 10N 0N Applied Force Net Force Vector sum of all forces exerted on an object

7. Experiment A motion diagram for the cart A free-body diagram for the cart Force and Motion Steadily push the back of a cart along a smooth surface so that it moves faster and faster Stop pushing the cart and let it coast. The cart does not slow down Push gently on the front of the moving cart so that it moves slower and slower F HonC F EonC F TonC F fr F EonC F TonC F HonC F EonC F TonC F fr

8. Force and Motion The object always changes its motion in the direction of the net force. The direction of the acceleration is in the same direction as the net force.

9. Aristotle: The normal state of objects is one of rest Galileo: ??? Slope downward – speed increases Slope upward – speed decreases No slope – does the speed change? Force and Motion Galileo Galilei (1564 – 1642)

10. Initial position Final position Where is the final position? Aristotle: The normal state of objects is one of rest Galileo: ??? Galileo Galilei (1564 – 1642)

11. Galileo Galilei (1564 – 1642) Galileo: There is property of a moving object to continue moving. This property called inertia Newton’s First Law Every object continues in its state of rest, or uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it. Isaac Newton (1642 - 1727)

12. Mass The greater the mass of an object the greater its inertia [m] = kg Mass ≠ Weight Weight of an object is the force of gravity acting on the object [W] = lb N

13. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks? (A) (B) (C) (D) (E)

14. No Homework!!! Hurray!!! No Quiz!!!