Universal Law of Gravitations, Statics, Coulomb’s Law Tuesday, February 9, 2016

Tuesday, 2/9  How are the forces of gravity and the forces that keep the planets rotating around the sun similar? How are they different? Upcoming dates:  Thursday, 2/12 – Statics quiz  Tuesday, 2/16 – Series circuit quiz  Thursday, 2/17 – Parallel circuit quiz  Monday, 22 – Circuit design due  Wednesday, 2/24 – Unit quiz  Friday, 2/26 – Electricity Test and missing work deadline  Thursday, 3/3 – Magnetism quiz  Friday, 3/4 – 3NWS Extra credit due by 4:00 PM  Wednesday, 3/9 – Waves Quiz  Friday, 3/11 – End of the 3NWS

Law of Universal Gravitation

Guiding Notes  What is the Universal Law of Gravitation?  What is the formula for analyzing Universal Law of Gravitation?  Describe what ‘G’ is and it’s value? Will the numerical value ever change?  How do you measure the distance between two objects?

Newton’s Universal Law of Gravity  Legend has it that Newton was struck on the head by a falling apple while napping under a tree. This prompted Newton to imagine that all bodies in the universe are attracted to each other in the same way that the apple was attracted to the Earth.  Newton analyzed astronomical data on the motion of the Moon around the Earth and stated that the law of force governing the motion of the planets has the same mathematical form as the force law that attracts the falling apple to the Earth.

Newton’s Universal Law of Gravity  Newton’s Law of Gravitation: every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Newton’s Law of Universal Gravitation The Gravitational Force is equal in magnitude, but opposite in direction which pulls the objects together d The distance d between m 1 and m 2 is measured from the center of m 1 to the center of m 2.

Review Equation  What does the G in the equation mean? Will it ever change?  Describe the relationship between mass and distance between the objects.  What variable has greatest role in evaluating the force of gravity between objects? Support your answer

Practice Problem 1 Tom has a mass of 70.0-kg and Sally has a mass of 50.0-kg. Tom and Sally are standing 20.0m apart on the dance floor. Sally looks up and sees Tom. She feels an attraction. If the attraction is gravitational, find its size. Assume that both Tom and Sally can be replaced by spherical masses.

Practice Problem 2  What is the gravitational attraction between two spheres ( m sphere = 1.67 X kg) at a distance of 5.0 X m? 7.44 x N

Practice

Activity  On the back lab tables you will find a ruler, a coffee filter, and small pieces of paper.  Your task is use the only supplies given and move the paper with the ruler without the ruler touching the table.  When you have completed your task respond the following on your cool down sheet:  What procedure did you use to move the paper?  What forces could you see? What forces were invisible?

Introduction to Static Electricity  Access the video link on my website for today.  Complete the video note guide while watching the video.  When finished show me your notes and I will record your grade.

Induction/Conduction guiding questions (6 minutes)  What circumstances must be present for conduction to take place?  What type of charge is transferred during the process of conduction ?  Draw the diagram that demonstrates conduction.  What circumstances must be present for induction to take place?  What type of charge is transferred during the process of induction ?  Draw the diagram that demonstrates induction.

Coulomb’s Law guiding questions (6 minutes  Explain the affect the value of the charges and and the distance of the charges has on the electrical force.  Write Coulomb’s equation and label the variables (include units).  How do you convert micro coulomb’s ( μC) to coulombs  What does the value of F electric tell you about the charges attraction/repulsion?  Set up the G and U for example #1.

Practice

Article – Shocking idea  Number your paragraphs (there should be 8).  Highlight the following words:  Electricity (all versions such as electric)  Shock  Charge  Static  Positive  Negative  Neutral  Friction  Circle words you don’t know the meaning of.  Underline statements about static electricity.

Socratic Seminar  Purpose; discuss academic text in a scholarly manner  One person talks at a time (must be holding the duck to talk).  Before you talk you must  Acknowledge what the previous person said and reference the text.  We will use the pilot, co-pilot format.

Dialogue is NOT Debate!

Pilot/Co-Pilot 1. Only pilots talk 2. Co-Pilots communicate With sticky notes.

Socratic Seminar