Untitled Flashcards Set

Recap of the course to date 2 Definition and Formula sheet Formulas • 𝑣 𝑡 =𝑣 , +𝑎𝑡 • 𝑥𝑡 =𝑥+𝑣 , 𝑡+⁄𝑎𝑡 • 𝑣 , =𝑣 , +2𝑎∆𝑥 • 𝑔= 9.8 m/s² • ∆⃗ 𝑝=⃗ 𝑝−⃗ 𝑝=0 • ∆𝑈 =𝑚𝑔∆𝑦 Definitions • ∆⃗ 𝑟≡⃗ 𝑟 −⃗ 𝑟=⃗ 𝑟(𝑡)−⃗ 𝑟(𝑡) • ⃗ 𝑣≡ lim ∆→ ∆⃗ ∆ 𝑣=⃗ 𝑣 =∆⃗ ∆ • 𝑎=⃗ 𝑎 ≡∆ ∆ • ⃗ 𝑝≡𝑚⃗ 𝑣 • K≡⁄𝑚𝑣 • E≡K+Eint • Emech≡K+U 3 Definition and Formula sheet Formulas • 𝑣 𝑡 =𝑣 , +𝑎𝑡 • 𝑥𝑡 =𝑥+𝑣 , 𝑡+⁄𝑎𝑡 • 𝑣 , =𝑣 , +2𝑎∆𝑥 • 𝑔= 9.8 m/s² • ∆⃗ 𝑝=⃗ 𝑝−⃗ 𝑝=0 • ∆𝑈 =𝑚𝑔∆𝑦 Definitions • ∆⃗ 𝑟≡⃗ 𝑟 −⃗ 𝑟=⃗ 𝑟(𝑡)−⃗ 𝑟(𝑡) • ⃗ 𝑣≡ lim ∆→ ∆⃗ ∆ 𝑣=⃗ 𝑣 =∆⃗ ∆ • 𝑎=⃗ 𝑎 ≡∆ ∆ • ⃗ 𝑝≡𝑚⃗ 𝑣 • K≡⁄𝑚𝑣 • E≡K+Eint • Emech≡K+U • 𝑣 𝑡 =𝑣 , +𝑎 𝑡 • 𝑦𝑡 =𝑦+𝑣 , 𝑡+⁄𝑎 𝑡 • 𝑣 , =𝑣 , +2𝑎∆𝑦 4 11/23/20 Chapters 1-3 • Essentially describing motion § Displacement § Velocity § Acceleration • Predictive tool: kinematic equations (for constant acceleration) Chapter 4: Momentum • Observation: before and after collisions 𝑚 𝑚 =−∆𝑣 ∆𝑣 • Concept introduced: momentum ⃗ 𝑝 ≡ 𝑚⃗ 𝑣 • System defined § Isolated system: where momentum is conserved. 5 6 Chapter 5: Kinetic Energy • Observation: reversible and irreversible collisions § Elastic and inelastic collisions • Concept: kinetic energy K ≡ ⁄𝑚𝑣 • Closed system: conservation of energy Chapter 7: Interactions • Observation: disappearing kinetic energy • Elastic and inelastic collisions • Concept: potential energy § Gravitational § Elastic 7 • Conservation of mechanical energy (Emech ≡ K+U): ∆Emech = 0 8 2 11/23/20 3 Going forward • Combined description •Why do we need another description?? 9 2 steps 1) transfer of momentum (at contact) 2) K⟺𝑈 Non-dissipative interaction: reversible (Newton’s cradle keeps going and going) 10 2 steps 1) transfer of momentum (at contact) 2) K⟺𝑈 Non-dissipative interaction: reversible (Newton’s cradle keeps going and going) Would it keep going forever? Why would it stop? 11 23 steps 1) transfer of momentum (at contact) 2) K⟺𝑈 Non-dissipative interaction: reversible (Newton’s cradle keeps going and going) Would it keep going forever? Why would it stop? • Seems non-dissipative on short timescales • Does not carry on forever • Actually dissipative interactions § Air resistance (friction) 12 11/23/20 4 Going forward • Combine everything into one theory §Newtonian Mechanics aka Newton’s laws §Not covering everything in detail §Concept introduced: forces 13 Forces • Abstract concept §Does not cause the motion... §Motion is caused by objects, but ... §Objects exert forces • Thus forces can describe the motion §Much more versatile description, §Every object is treated on same footing §Irrespective of physical attributes 14 PHYS101 Pedagogy Knowing and understanding • Knowing Newton’s Laws is differ from understanding them Delayed introduction of forces and Newton’s Laws to • give a fuller picture, • in-depth motivation, • make the application more intuitive. 15 Recap of the video • Orientation with regards what we have done, and, •where we are going. 1