1. Physics 1100 – Spring 2012 Inertia, Forces and Acceleration: The Legacy of Sir Isaac Newton Objects in Motion

2. Physics 1100 – Spring 2012 Chapter 2 - Newton’s First Law of Motion - Inertia Aristotle on Motion Copernicus and the Moving Earth Galileo and the Leaning Tower Galileo's Inclined Planes Newton’s First Law of Motion !!! Net Force The Equilibrium Rule Support Force Equilibrium of Moving Things

3. Physics 1100 – Spring 2012 A Little History Aristotle (~320 BC) –Air, earth, fire, water –Unnatural motion – Horizontal motion –Testing of theories not considered needed so his ideas lasted for 2000 years. Galileo Galilei (~1640) –Provided new theories based on observation and experiment. –Stones twice as heavy do not fall twice as fast as Aristotle said –Experimented with balls and incline planes –Inertia! Isaac Newton (~1700) –Three laws of motion –Laws of gravitation –Greatest scientific book: Principia Mathematica Philosophiae Naturalis - 1687

4. Physics 1100 – Spring 2012 Galileo and Falling Bodies

5. Galileo and Inclined Planes Physics 1100 – Spring 2012

6. Inclined Planes and Inertia

7. Physics 1100 – Spring 2012 Newton’s 1st law - Inertia If the total “resultant” force acting on an object is zero, the object will either remain at rest or it would move along a line with a constant velocity.

8. Physics 1100 – Spring 2012 Newton Says A ball sitting still will stay that way, unless acted upon by a force. An object that is not subjected to any outside forces moves at constant velocity, covering equal distances in equal times, along a straight path, x(t) = x(0) + vt Newton’s 1 st Law Inertia Mass This is not intuitively obvious.

9. Physics 1100 – Spring 2012 Examples of Inertia

10. Physics 1100 – Spring 2012 Force Has Direction!

11. Net Force Physics 1100 – Spring 2012

12. Stable Equilibrium,  F = 0 Physics 1100 – Spring 2012

13. A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is: A) more than 30 m/s. B) zero. C) about 30 m/s. D) less than 30 m/s but larger than zero. E) More information is needed for an estimate.

14. Physics 1100 – Spring 2012 Whirl a rock at the end of a string and it follows circular path. If the string breaks, the tendency of the rock is to A) follow a straight-line path. B) continue to follow a circular path. C) revolve in a smaller circle D) increase its speed

15. Physics 1100 – Spring 2012 If no external forces are acting on a moving object it will A) continue moving at the same velocity. B) continue moving at the same speed. C) move slower and slower until it finally stops.