1. Dynamics: Intro Physics 11

2. What is dynamics?  area of Physics  Is the branch of mechanics concerned with the forces that cause motions of bodies  What is a body?  physical body or physical object (usually called a body or object) is a collection of masses taken to be one. For example, a basket ball can be considered an object but the ball also consists of many particles (pieces of matter).  Force = push or pull

3. How are kinematics and Dynamics related?  The study of the causes of motion and changes in motion is dynamics. In other words the study of forces and why objects are in motion.  In contrast kinematics, describes only the motion of objects without consideration of the causes leading to the motion.

4. This guy named Newton….  1643 – 1727  Started the groundwork for most of classical mechanics.  Newton described universal gravitation and the three laws of motion which dominated the scientific view of the physical universe for the next three centuries.  Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws by demonstrating the consistency between Kepler's laws of planetary motion and his theory of gravitation, thus removing the last doubts and advancing the Scientific Revolution.  We’ll come back to Newton….

5. But first Galileo:  He, like many, attempted to understand why objects move or remain at rest

6. Galileo…  His experiment challenged the commonly held belief, at that time, that an object motion was the result of a continued force  Instead, he viewed motion as a state just as natural as rest  He had identified the natural tendency of mass to continue what it is already doing…continue in motion or stay at rest  He was defining inertia, he ideas were not immediately accepted but his concepts of inertia have stood the test to time!

7. Inertia:  Is the natural tendency of an object to remain in its current state of motion  The amount of an objects inertia is directly related to its mass.  “An object in motion will remain in motion or an object at rest will remain at rest until acted upon by an external force.” Newton’s First Law

8. Inertia = Mass Bigger masses have more… Smaller masses have less inertia.

9. Which is harder to stop? The larger mass has more inertia. It has more resistance to changes in motion!

10. Practise:  Pg 129 #1, 2, 3, 4