lecture2

# lecture2 - Lecture 2 Kinematics 1 Review from Last Time...

This preview shows pages 1–2. Sign up to view the full content.

Lecture 2 Kinematics 1 Review from Last Time Vector Manipulation Important point: the magnitude of the difference between two vectors is not equal to the difference of their magnitudes!!! (Section III on Vector Worksheet). Example: Two people push on the desk from opposite sides. If we want to know how the desk moves under the net force acting on it, we need to add the forces. But force is a vector and includes direction! If each person exerts a force of magnitude 5N, but they push in opposite directions, obviously the desk won’t accelerate. This is because if we add the two vectors , the magnitude of the sum of the two forces is zero. Conceptually, it’s obvious that the desk won’t accelerate, but vectors allow us to keep track of direction (which is clearly important) and get the right answer mathematically. This will help us solve problems that are more complicated and not quite so obvious as this example! 2 Kinematic Definitions A few final preliminaries .... you’ve all been introduced to concepts like velocity and acceleration before (either in a physics class or just everyday life). We have very precise definitions of these in physics that are important (and somewhat suprisingly subtle). In order to describe the motion of an object, we need to be clear on these definitions. That’s the basic idea of kinematics - a mathematical description of an object’s motion. A bunch of people thought the relation between displacement, velocity, and acceleration was interesting. So, I’ll define them here again using vectors so you can get comfy with notation. I’ll also point out what I think is interesting! 2.1 Displacement We describe the position of an object by a single point. Of course, an object like a car or a person is not a single point! But, we describe their position that way anyway. We might think of representing the position of the car by the location of its center, for example. (DRAW person with pt at center) the position vector of an object, vector r , has a length (magnitude) equal to the distance of the object from the origin, and it points from the origin to the object. Thus the position vector depend on the choice of coordinate system!

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern