Classical Mechanics Lecture 5 - Free Body Diagrams & Forces

Oct 29, 2026

Lecture 5 on classical mechanics introduces key tools and force models used to analyze motion. It focuses on free body diagrams, including forces from strings, springs, and gravity, and connects these ideas to common multi-dimensional problem setups. The lecture also provides an extended intuitive explanation of hurricane rotation, linking apparent turning direction to rotating frames, Earth’s rotation, pressure gradients, and resulting counterclockwise rotation in the northern hemisphere.

LanguageEnglish

CategoryExam

FormatPDF

Pages21

Reading Time53 min

AccessFree to download

Today’s Concepts

Free Body Diagrams

Forces: Strings, Springs, Gravity

Hurricane Explanation

Classical Mechanics Lecture 5 Today’s Concepts: a) Free Body Diagrams b) Force due to strings c) Force due to springs d) Force due to gravity Mechanics Lecture 5, Slide 1 Stuff you asked about: 􀀡 S"ll easier than instant cake mix . 􀀡 A problem like the elevator problem, but in two dimensions or even 3 dimensions . So maybe the elevator is from Willy Wonka's factory, and can move in 3 dimensions 􀀡 elevators are pre@y messed up~! 􀀡 Universal law of Gravita"on is not very clear. plz explain and give some examples in the class :) 􀀡 I'd like to get more of an explana"on on force tension in situa"ons with objects like hanging masses on a string. 􀀡 Why gravita"onal force is so small compared to the other major forces? 􀀡 one does not simply understand free body diagrams (FBD's) in one night. [h@p://www.quickmeme.com/meme/3rb28i/](h@p://www.quickmeme.com/meme/3rb28i/) 􀀡 so far so good. i love physics! 0.0 Mechanics Lecture 5, Slide 2 Hurricane explanation We observe that hurricanes rotate CCW in the northern hemisphere, CW in southern hemisphere . Mechanics Lecture 5, Slide 3 Hurricane explanation 1) If you are on some object rotaJng clockwise then objects moving in a straight line relaJve to someone who is not rotaJng appear to be turning LEFT relaJveto you . 2) If you are on some object rotaJng counter clockwise then objects moving in a straight line relaJve to someone who is not rotaJng appear to be turning RIGHT relaJve to you . Mechanics Lecture 5, Slide 4 Hurricane explanation 3) Viewed from above the North Pole, the earth is rota7ng counterclockwise . This means if you are in the northern hemisphere, things will always appear to be turning right. SUN Mechanics Lecture 5, Slide 5 Hurricane explanation 4) The atmospheric pressure at the center of a hurricane is much lower than the atmospheric pressure in the air surrounding it. This means that air tries to move from the outside to the inside . Mechanics Lecture 5, Slide 6 Hurricane explanation 5) Since the earth is rotaJng, all of these lines will turn to the right as they move toward the center. Mechanics Lecture 5, Slide 7 Hurricane explanation 6) All of these “right turns” make the hurricane rotate CCW. Mechanics Lecture 5, Slide 8 Mechanics Lecture 5, Slide 9 Mechanics Lecture 5, Slide 10

FAQs

What does Lecture 5 focus on in classical mechanics?

It covers free body diagrams and how to model forces from strings, springs, and gravity, along with an intuitive hurricane rotation explanation related to rotating frames.

How are forces due to strings, springs, and gravity treated in the lecture?

The lecture lists these as core force types under the umbrella of mechanics modeling, meant to be used with free body diagrams for problem solving.

Why do hurricanes rotate differently in the northern and southern hemispheres according to the lecture?

It explains the observed rotation direction using Earth’s rotation, apparent turning in a rotating reference frame, and a pressure difference that drives air inward, then notes that consistent “right turns” lead to counterclockwise rotation in the northern hemisphere.

Oct 29, 2026

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