Physics 121, Sections 9, 10, 11, and 12 Lecture 3 Announcements Lectures available on the web(short version) For over-enrollment please go to the physics office P107 aboratory sessions start next week Gotomywebsitewww.phys.uconn.edu/-rcote Syllabus t homeworks lectures, etc WebAssign gotowww.webassign.netandlogin username: first letter of first name plus last name e.g. John Fernando Lachance: lachance 》 institution: uconn > password: People Soft ID#(without the initial") Physics 121: Lecture 3, Pg 1
Physics 121: Lecture 3, Pg 1 Physics 121, Sections 9, 10, 11, and 12 Lecture 3 Announcements Lectures available on the web (short version) For over-enrollment please go to the Physics office P107 Laboratory sessions start next week Go to my web site www.phys.uconn.edu/~rcote Syllabus + homeworks + lectures, etc. WebAssign: go to www.webassign.net and log in » username: first letter of first name plus last name » e.g. John Fernando Lachance: jlachance » institution: uconn » password: PeopleSoft ID # (without the initial “0”)
Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Today's Topics Homework 1: Due Friday Sept 6 @6: 00PM Ch.1:#4,10,14,19,31,and33 Ch.2:#1.23,37,and63 Chapter 2 Forces and vectors Types of forces Newton's Laws of motion Net force and vector addition Contact force and tension Chapter 3: Forces and motion along a line Position, velocity, acceleration Physics 121: Lecture 3, Pg 2
Physics 121: Lecture 3, Pg 2 Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Today’s Topics: Homework 1: Due Friday Sept. 6 @ 6:00PM Ch.1: # 4, 10, 14, 19, 31, and 33. Ch.2: # 1, 23, 37, and 63. Chapter 2: Forces and vectors Types of forces Newton’s Laws of motion Net force and vector addition Contact force and tension Chapter 3: Forces and motion along a line Position, velocity, acceleration
Problem solution method Five steps: 1) Focus the Problem draw a picture- what are we asking for? 2)Describe the physics what physics ideas are applicable what are the relevant variables known and unknown 3) Plan the solution what are the relevant physics equations 4)Execute the plan solve in terms of variables solve in terms of numbers 5) Evaluate the answer are the dimensions and units correct? do the num bers make sense? Physics 121: Lecture 3, Pg 3
Physics 121: Lecture 3, Pg 3 Problem Solution Method: Five Steps: 1) Focus the Problem - draw a picture – what are we asking for? 2) Describe the physics - what physics ideas are applicable - what are the relevant variables known and unknown 3) Plan the solution - what are the relevant physics equations 4) Execute the plan - solve in terms of variables - solve in terms of numbers 5) Evaluate the answer - are the dimensions and units correct? - do the numbers make sense?
Chap 2: Forces and vectors In classical mechanics Need to study interactions between objects Described by forces We have an idea of what a force is from everyday life Physicist must be precise A force is that which causes a body to accelerate (See Newton's Second Law) A Force is a push or a pull A Force has magnitude& direction(vector) F Physics 121: Lecture 3, Pg 4
Physics 121: Lecture 3, Pg 4 Chap.2: Forces and vectors In classical mechanics Need to study interactions between objects Described by forces We have an idea of what a force is from everyday life. Physicist must be precise. A force is that which causes a body to accelerate. (See Newton’s Second Law) A Force is a push or a pull. A Force has magnitude & direction (vector). F
Fundamental Forces Example of Forces Hooke' s law for ideal spring: F=-kX Units of a force are 1 N 1 kg m/s 2 Fundamental Forces Gravity(more later) >) For motion of planets, etc Strong and weak nuclear forces(not here !) >)Explains behavior of nucleus in atoms Electromagnetic force(next semester in PHY122) >)Relevant for electric systems, chemical properties, etc Physics 121: Lecture 3, Pg 5
Physics 121: Lecture 3, Pg 5 Fundamental Forces Example of Forces Hooke’s law for ideal spring: F = -k x Units of a force are 1 N= 1 kg m/s2 Fundamental Forces Gravity (more later) »For motion of planets, etc. Strong and weak nuclear forces (not here !) »Explains behavior of nucleus in atoms Electromagnetic force (next semester in PHY122) »Relevant for electric systems, chemical properties, etc