BELL RINGER 12/8: Summarize what you did in Tuesday’s collision

activity.

OBJECTIVE: SWBAT define conservation of momentum; SWBAT define and calculate for inelastic collisionsAGENDA: • Notes• Group Practice• Exit Ticket

HOMEWORK: 1-5, 7-8a on Worksheet

Conservation of Momentum

• Momentum in a system is conserved• Pfinal=Pinitial

• In general, for two objects that are colliding, the equation looks like:

m1v1 + m2v2 = m1v1 + m2v2

But, the equation is rearranged or changes slightly depending on the type of collision!

initial final

Applying conservation of momentumEX: Two ice skaters meet in the center of the rink and come to rest. They now push off against one another. One skater, with a mass of 54-kg, acquires a speed of 0.95 m/s. What is the speed of the other skater, whose mass is 61-kg?

Conservation of Momentum + Collisions

• Momentum in the system (objects colliding) is conserved as long as there are no external forces acting on the system

• That doesn’t mean momentums within the system don’t change; the sum remains the same, but momentum will transfer b/w objects

COLLISIONSThere are two types of collisions:1.Inelastic: momentum is conserved, but kinetic energy is not; objects stick together upon collision. When the maximum amount of KE is lost to other forms of energy, it is called a completely inelastic collision. 2. Elastic: momentum and kinetic energy are conserved

INELASTIC COLLISIONSWhen one object starts at rest and the objects stick together after the collision and have the same final velocity, the equation is rearranged to:

m1v1 + m2v2 = m1v1 + m2v2

m1v1 = (m1 + m2) v

Note: one object won’t always start at rest, so the m2v2

term can come back!

INELASTIC COLLISIONSEX: On a touchdown attempt, a 95.0-kg running back runs to the right towards the end zone at 3.75 m/s. An 111-kg linebacker moving to the left at 4.10 m/s meets the runner in a head-on collision. If the two players stick together, what is their velocity immediately after the collision?

BELL RINGER 12/5: Answer Choices for Question 4:STANDARD: EMI 601

OBJECTIVE: SWBAT solve collision problems using the conservation of energy equationsAGENDA: • Group Practice• Start Problem Set

HOMEWORK: Problem Set due Monday (check your email); QUIZ MONDAY!

BELL RINGER 12/5:

What is the general equation for conservation of momentum?

OBJECTIVE: SWBAT solve collision problems using the conservation of energy equationsAGENDA: • Group Practice• Start Problem Set

HOMEWORK: Problem Set due Monday (check your email); QUIZ MONDAY!

REVIEWA train with a mass of 3500-kg is traveling at 20 m/s when it collides with another train that has a mass of 2700-kg and is traveling 15 m/s. If the objects stick together upon collision, what will be the trains’ velocity right after colliding?

GROUP PRACTICE