Get started today!

Good to have you back!
If you've signed in to StudyBlue with Facebook in the past, please do that again.

- StudyBlue
- Kansas
- University of Kansas
- Physics
- Physics 114
- Ammar
- Lecture Notes 10/6

Anonymous

Advertisement

Lecture Notes October 6th Elastic Collisions/CM Bold letters indicate vectors Inelastic Collisions Kinitial ≠ KFinal Pinitial= Pfinal Elastic Collisions Kinitial = KFinal Pinitial= Pfinal If masses are equal, when m1 hits m2; m1 will stop and m2 will continue with its (m1’s) velocity. If masses aren’t equal, the object at rest will be set in motion with some v and the other will recoil (ball thrown against a wall) Elastic Collisions in 1 dimension Before After Va Vb V’a V’b ma mb ma mb Ki = KF => ½mava2 + ½mbvb2 = ½mav’a2 + ½mbv’b2 Pinitial= Pfinal => mava + mbvb = mav’a + mbv’b When given: ma, Va, mb, Vb - you are able to find V’a and V’b You find the following results : (Va - Vb) = -(Va’ - Vb’) The relative velocity of A & B with which they approach each other equals the relative velocity with which they recede from each other. Example – 2 equal Masses ma = mb = m Vb = 0 Equation 1 = Ki = Kf Equation 2 = Pi = Pf Equation 3 = (Va - Vb) = -(Va’ - Vb’) mava + mbvb = mav’a + mbv’b va + 0 = v’a + v’b Equation 4 = va = v’a + v’b Equation 5 = Va = -V’a + V’b Eq. 4 - Eq. 5 => 0 = 2V’a + 0 => Equation 6 = V’a = 0 (projectile stops) Plug 6 into 4 to get: Equation 7 = Va = Vb (target takes on velocity of projectile) Center of Mass Xcm = (m1x1 + m2x2 + m2x2) / m1 + m2 + m3 Ycm = (m1y1 + m2y2 + m3y3) / m1 + m2 + m3 General CM = Σmix2 ÷ Σmi - Center of mass for objects with a high degree of symmetry can usually be guessed. (sphere) - If no external forces act, the center of mass cannot move => CM is fixed. Example A child pulls a sled towards him (on frictionless ice) until they meet. How far does the child move? mchild = 30 kg msled = 5 kg d = 10 m Xcm = 30(0) + 5(10) / 35× Xcm = 50/35 Xcm = 1.43 m 10 m = child = sled Example - Projectile Shoot off a rocket with mass m that explodes at the height of its flight. It is separated into 2 equal parts. CM d d d Example - Raft As you walk from one end to the other, the boat must move to the left in order to keep its CM in the same location.

Advertisement

"StudyBlue is great for studying. I love the study guides, flashcards and quizzes. So extremely helpful for all of my classes!"

Alice , Arizona State University"I'm a student using StudyBlue, and I can 100% say that it helps me so much. Study materials for almost every subject in school are available in StudyBlue. It is so helpful for my education!"

Tim , University of Florida"StudyBlue provides way more features than other studying apps, and thus allows me to learn very quickly!??I actually feel much more comfortable taking my exams after I study with this app. It's amazing!"

Jennifer , Rutgers University"I love flashcards but carrying around physical flashcards is cumbersome and simply outdated. StudyBlue is exactly what I was looking for!"

Justin , LSU