{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture214Week3

Lecture214Week3 - What causes motion In our everyday life...

This preview shows pages 1–8. Sign up to view the full content.

05/11/09 Physics 214 Fall 2008 1 What causes motion In our everyday life we observe that objects change their state of motion. In fact everything that happens in the Universe results from a change in motion. That is a static inert object does not contribute to any of the things we consider to be useful. The functioning of our body depends on continual change throughout our bodies. These changes are produced by forces and in our everyday life there are just two forces. Gravity acts on mass Electric charge

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

View Full Document
05/11/09 Physics 214 Fall 2008 2 Newtons Second and First Law Second Law The acceleration of an object is directly proportional to the magnitude of the imposed force and inversely proportional to the mass. The acceleration is in the same direction as the force F = ma F and a are vectors unit is a Newton (or pound) 1lb = 4.448N First Law An object remains at rest or in uniform motion in a straight line unless it is acted on by an external force . F = 0 a = 0 so v = constant http://www.physics.purdue.edu/academic_programs/courses/phys214/movies.php ( anim0003.mov) (anim0004.mov)
05/11/09 Physics 214 Fall 2008 3 Force at the earths surface r E

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

View Full Document
05/11/09 Physics 214 Fall 2008 4 Mass and weight Newtons second law enables us to measure relative mass. If we apply the same force to two objects and measure the accelerations then. F = m 1 a 1 and F = m 2 a 2 so m 1 /m 2 = a 2 /a 1 We then need to have one mass as a calibration and a kilogram is the mass of a piece of platinum held in Paris. Since gravity acts proportional to mass then the force near the earths surface is F = mg this is the weight of an object so if we compare
05/11/09 Physics 214 Fall 2008 5 Inertia Inertia = tendency of an object to resist changes in its velocity. Since F = ma and a = Δv/t then Ft = mΔv So if a force acts for a time t the change in velocity will be smaller for larger masses so it is mass that determines inertia. In particular if t is very small and m is large then F can also be large but Δv can still be very small .

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

View Full Document
05/11/09 Physics 214 Fall 2008 6 Friction In our everyday world any object which is moving feels a force opposing the motion --- this is friction. An object which is sliding The air resistance on your car These types of friction result in energy being lost and minimizing friction is very important. But Friction is also useful and essential since with no friction a car would not move but just spin it’s wheels a car would not be able to turn a corner we would not be able to walk objects would slide off surfaces unless perfectly horizontal
05/11/09 Physics 214 Fall 2008 7 Force diagrams When we are analyzing a particular object we have to take into account all the forces acting on the body both in magnitude and direction. The acceleration of the object is equal to F/m in the direction of F where F is the net force acting.

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