Chapter_9 - 2 x 1 x y P total = constant (if F total ext =...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Ch 9: Linear Momentum and Collisions Focus: Systems of Particles, Conservation of Momentum Systems of Particles: F 1 M 1 1 particle: = Total force on M 1 -- determines motion 2 particles: M 2 F 12 F 1ext M 1 F 21 F 2ext 2 on 1 1 on 2 Distinguish internal forces between particles, F 12 and F 21 , from external forces: ext dt d M 1 21 1 1 1 F F F v + = = ext dt d M 2 12 2 2 2 F F F v + = = = 0, 3 rd Law Total external force () ext ext M M dt d 2 1 ) 12 21 2 2 1 1 ( F F F F v v + + + = + add
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Ch 9: Linear Momentum and Collisions Focus: Systems of Particles, Conservation of Momentum Memorize this! Define the Momentum: v p M = 2 2 2 1 1 1 , v p v p M M = = i.e., 1 particle: total dt d 1 1 F p = ext total dt d F P = total or 2 1 total p p P + = where Memorize this! If F total ext = 0 , then P total = constant Memorize this! () ext total ext ext dt d F F F p p = + = + 2 1 2 1 2 particles: Total external force determines rate of change of total momentum Vector Momentum Conservation
Background image of page 2
Ch 9: Linear Momentum and Collisions Focus: Collisions and Center of Mass Rules for Collisions For 1, what is conserved if masses bounce, stick? For 2, what is conserved if the blue mass slides down without friction? Total momentum for both cases, Total kinetic energy for bounce
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 2 x 1 x y P total = constant (if F total ext = 0): Vector equation (x,y,z components) 1) Total mass conserved 2) If elastic (bounces, slides), total energy conserved : Scalar equation 3) If inelastic (sticks) only P total conserved if F total ext = 0 4) Ch 9: Linear Momentum and Collisions Center of Mass 2 2 1 1 CM r r r m m M + ≡ M = m 1 + m 2 = total mass r CM is the mass weighted position vector or center of mass Why do this? Key idea: The center of mass acts like one particle at r CM acted on by total external force total m m M M dt d P v v v r = + = = 2 2 1 1 CM CM external total total M dt d F a P = = CM Example: Find r CM , a CM if: r 1 = 1 i , m 1 = 1 kg; r 2 = 2 j , m 2 = 2 kg F 1 = 2 N j F 2 = 1N i j i r 2 2 ˆ 1 1 3 CM ⋅ + ⋅ = m 3 1 CM = x m 3 4 CM = y j i a 2 ˆ 1 3 CM + = 2 3 1 xCM m/s = a 2 3 2 yCM m/s = a...
View Full Document

This note was uploaded on 05/13/2010 for the course PHYSICS 53L taught by Professor Mueller during the Fall '07 term at Duke.

Page1 / 4

Chapter_9 - 2 x 1 x y P total = constant (if F total ext =...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online