Module 5: Circular Motion and Newtonian Gravity

Module 5: Circular Motion and Newtonian Gravity

Introduction

Much of what we have covered so far has involved motion in one dimension. When we have considered two-dimensional motion, we have taken it to be the superposition of two, one-dimensional problems. However, much of the motion we see around us is in the form of circles, and it not easy to separate into x and y axes. Mathematically, motion in circles is rather different from motion in straight lines, but the underlying laws of physics are the same.

Learning Objectives

Upon completion of this module, students will be able to: 

  • Extrapolate linear motion to circular motion
  • Calculate the acceleration of an object moving at uniform speed in a circle
  • Identify centripetal forces 
  • Apply Newton's Universal Law of Gravitation to solve for the force between two masses
  • Explain how Newton's Universal Law of Gravitation relates to the orbits of satellites and the uniform value of "g" at the earth's surface
  • Explain the concept of "weightlessness"
  • Identify how measurements of "weight" can be misleading
  • Explain the origin of tides
  • Express how circular motion and Newtonian gravity can be seen in daily occurrences 

To Do List

1. Watch Video Lectures (links below)
2. Complete the Practice Problems(links below)
3. Take the Module 5 Quiz
4. Complete the Exam Practice Problems for Module 5

Video Lectures

Lesson 5.1 Circular Motion and Centripetal Acceleration 

In this lesson the equation, a=v2/r   for circular motion at uniform speed is introduced and the centripetal and centrifugal forces are explained.

Lesson 5.2 Newton's Universal Law of Gravitation

Newton's Universal Law of Gravitation, one of the basic laws of physics, is explained. Examples are done to show how this law leads to stable orbits for satellites at any distance from a planet or star as well as explaining our value of "g". The laws of proportionality are shown to be useful in solving problems to do with orbits.

Lesson 5.3 Applications of Universal Law of Gravitation

Weightlessness is a word that we use frequently, but here we discuss the physics meaning of the word. We show examples of a man standing in an elevator standing on a bathroom scales and moving and/or accelerating up or down. Lastly we cover the origin of tides, and how the sun and the moon both affect our tides and why.

Quiz

Once you have watched the lectures and completed the practice problems, you should demonstrate your understanding by taking the Module 5 Quiz. Be sure to submit the quiz before its deadline.

Coming Up 

In the next module we will learn about Work and Energy and after that you will have your first exam. The Exam 1 Review is already available.