TODAY Today's Goal: 1) New topic: Impulse and Momentum. Lets start learning about Impulse 2) Apply our idea to collisions through graphs. Homework: Given out. To make sure we can understand impulse through graphs and situations.

HW TURN IN Day 23 Day 24 Day 25

Plus a few from 1st quarter OUR BIG QUIZ Monday/Tuesday All Forces Plus a few from 1st quarter

No friction! Assume M2 goes down + -

Which of these is true for the amount of imbalance in the system? A) Its just W2 because the normal force on M1 cancels the weight B) Its W2 + W1x, the system weight are them combined C) Its W2 - W1x, the difference between the weights D) Its W2 + W1, since system weight are them combined

Which of these is true for the amount of imbalance in the system? A) Its just W2 because the normal force on M1 cancels the weight B) Its W2 + W1x, the system weight are them combined C) Its W2 - W1x, the difference between the weights D) Its W2 + W1, since system weight are them combined

As the angle increases, what will happen to the acceleration? A) It increases, since there is more gravitational pull B) It decreases, since there is more gravitational pull C) It decreases, since the weight of m1 is more vertical D) It increases, since the weight of m1 is more vertical

As the angle increases, what will happen to the acceleration? A) It increases, since there is more gravitational pull B) It decreases, since there is more gravitational pull C) It decreases, since the weight of m1 is more vertical D) It increases, since the weight of m1 is more vertical

If there was friction, which would be a correct relationship? A)max = m2g – m1gsinθ + μm1gcos θ B)max = m2g – m1gcosθ + μm1gsin θ C) max = m2g – m1gsinθ - μm1gcos θ D) max = m2g – m1gcosθ - μm1gsin θ

If there was friction, which would be a correct relationship? A)max = m2g – m1gsinθ + μm1gcos θ B)max = m2g – m1gcosθ + μm1gsin θ C)max = m2g – m1gsinθ - μm1gcos θ D)max = m2g – m1gcosθ - μm1gsin θ

CAREFUL! We now need to define systems and isolation. System: Two or more objects interacting Isolated System: No external imbalance of forces; 1) A force that is made from something outside the system 2) An unbalanced force

Our Major Ideas to Start In Words In Equation Units How its used Momentum, Symbol is p The motion of objects which involves both the mass and velocity. p = m*v Kg*m/s or a N*s In systems where two objects interact, momentum is conserved Momentum : Its like the overall motion of an object. Has direction.

Question Can do different masses have the same momentum? Sure! It depends on the velocities. Heavier mass must have less velocity. Which is larger, a momentum of -20N*s or +16kg*m/s? -20! Negative means direction.

Two Things Hitting: 1) How does force on the heavy truck compare to that of the car? A) The force on the truck is larger than on the car B) The force on the truck is equal to the cars force C) The force on the truck is less than on the car

Two Things Hitting: 1) How does force on the heavy truck compare to that of the car? A) The force on the truck is larger than on the car B) The force on the truck is equal to the cars force C) The force on the truck is less than on the car

Two Things Hitting: 2) How does the change in momentum of the heavy truck compare to that of the car? They are the same! Due to the conservation of momentum of this isolated system.

Two Things Hitting: 3) How does the change in velocity of the heavy truck compare to that of the car? The truck (which is heavier) will have less of a change in velocity from the same change in momentum (due to larger inertia)

No Math Required How large is the truck compared to the car (fraction or multiple) 3 times! So what fraction or multiple will it have compared to the cars change in velocity? 1/3! So how much did its velocity change by?

1/3 of 15, so it should DROP by 5 in this case! Resulting in a final velocity of 5! Lets prove it

Two Things Hitting: BEFORE THE IMPACT: SYSTEM MOMENTUM How much momentum does the truck and car have? TRUCK CAR SYSTEM MOMENTUM

Two Things Hitting: AFTER THE IMPACT: SYSTEM MOMENTUM BEFORE: How much momentum does the truck and car have? TRUCK CAR SYSTEM MOMENTUM BEFORE:

Two Things Hitting: SO HOW MUCH CHANGE IN MOMENTUM OCCURRED IN THE COLLISION?

Two Things Hitting: Now find the trucks new velocity from that change in momentum

Two Things Hitting:

Two Things Hitting: Lets graph the change in velocity for each!

SO FOR MOMENTUM IN A COLLISION OF 2 OBJECTS: ΔP of one object = ΔP of the other object System momentum before = System momentum after

Two Things Hitting: Using this…

Our example Car A has a mass of 1500kg and travels to the right at a speed of 20m/s. Car B travels left with a speed of 10m/s. After the vehicles collide, they stick together and move left with a common velocity of 5m/s. 1. Calculate the mass of Car B

Which car is heavier, A or B? LOGIC Which car is heavier, A or B?

How much did A change by? B? LOGIC How much did A change by? B? So whats the mass of B?

A Way To Organize

Idea: Compare the momentums before and after

Template Problems. 1)

Template Problems. 1)

Template Problems. 1)