Slide 1

Slide 2

Conservation of Momentum Review

Slide 3

Objective SWBAT recall, explain, and solve problems that test knowledge of physics concepts.

Slide 4

Week Schedule/Blog Double Block Today Single Block Tomorrow Questions/comments/concerns? Want to discuss a problem? Need help with something www.phaphysics.wordpress.com www.phaphysics.wordpress.com GO TO THE MIDTERM DISCUSSION BOARD I will respond promptly

Slide 5

Todays Agenda Conservation of Momentum Review Review Exercise

Slide 6

Why Conservation of Momentum? Objective: SWBAT solve conservation of momentum problems. 68.8% 83%

Slide 7

The Concept Conservation = Nothing is lost, nothing is gained. Usually we are talking about before a collision And after a crash

Slide 8

The Concept Before mv + = + P = MV

Slide 9

The Concept So, this notation that you see: p i = p f It means the total amount of momentum before a collision equals the total amount of momentum after the collision. Other ways we can write this: m i v i + m i v i = m f v f + m f v f m i v i + m i v i = (m f + m f )v f Object 1 Object 2Object 1Object 2

Slide 10

Two bowling balls are rolling towards each other on ice (assume no friction). Ball A has a mass of 5 kg and is moving to the right at 10 m/s. Ball B has a mass of 7 kg and is moving at 7 m/s. If the balls stick together after the collision, how fast do they move after they collide? 5 kg, 10 m/s AB 7 kg, -7 m/s

Slide 11

An air hockey puck (5kg) is moving at 8 m/s collides with another air hockey puck moving at 8 m/s. After the collision, both pucks are at rest. What is the mass of the second puck?

Slide 12

An air hockey puck (5kg) moving at 8 m/s collides with another air hockey puck moving at 8 m/s. After the collision, both pucks are at rest. What is the mass of the second puck?

Slide 13

You Try 2 Practice Problems We will then quickly go over them Following this, we will begin our review game!

Slide 14

Two bowling balls are traveling towards each other in outer space where there is no friction. Ball A has a mass of 9 kg and is moving in the positive direction at 14 m/s. Ball B has a mass of 4 kg and is moving at 6 m/s. If the balls stick together after the collision, how fast do they move after they collide? 9 kg, 14 m/s AB 4 kg, -6 m/s

Slide 15

A large truck (256 kg) is traveling east down the road at a speed of 54 m/s. It collides with a small car (134 kg) that is also traveling east, but slower, going only 12 m/s. If the two cars stick together after the collision, how fast are they moving?

Slide 16

Distributing Envelopes Everyone gets one. Dont open it until everyone has one!

Slide 17

Do Now: Split Up FRONT BACK MIT HARVARD

Slide 18

The Central Square Battle The Harvard Crimson versus The MIT Beavers Note: no longer mascot

Slide 19

Why The Battle? To fight over getting the highest grade on their midterms.

Slide 20

How Will They be Fighting? By a good old-fashioned game of Bluff.

Slide 21

How Does Bluff Work? Say Harvard is up first. A question will come up on the slideshow. Is velocity a vector or scalar quantity? Harvard students will be given a certain amount of time to come up with the answer. On their own, of course. Velocity is a vector, because it has direction. When times up, every Harvard student that thinks they know the answer can stand up.

Slide 22

So, now we have a bunch of Harvard kids standing around, that apparently know the answer. Ill randomly choose 1 MIT kid. He can choose any Harvard kid to share their answer. If he gets it right, Harvard gets a point for each person who was standing. If hes wrong, any MIT student can give me the answer. If hes right MIT gets the same # of points. How Does Bluff Work?

Slide 23

How Does Bluff Work No talking during problem-solving time. Minus 5 point penalty. You get to celebrate! For 10 seconds each round after you get 1 right. No talking during how-to-do-it time. I will quickly show how to solve Minus 5 point penalty. Winners??? Get a prize? What is it? Wait and see!

Slide 24

How Does Bluff Work? Whos going to win, Harvard or MIT?

Slide 25

First Team Up Harvard University! So they will solve problem I will choose a person from MIT to pick the Harvard person to share their answer. MIT should solve too! If Harvard gets it wrong you get a shot!

Slide 26

Silence Warning Remember to be silent during problem solving time!

Slide 27

Question 1 A 2 kg hockey puck is moving at 9m/s, how much momentum does the hockey puck have?

Slide 28

Question 2 A 100 kg car is traveling at 20 m/s. It then speeds up to 40 m/s. Calculate the impulse.

Slide 29

Question 3 A 20 kg bear is running at 10 m/s towards an unsuspecting 50 kg person who is not moving. They collide. If the bear and person stick together, what will their final velocity be?

Slide 30

Question 4 A 32 kg ice skater is traveling at +45 m/s towards a 5 kg hockey goal that is at rest. After she collides with the goal (they do not stick together), the goal moves with a speed of +36 m/s. What is the final velocity of the ice skater?

Slide 31

Question 1 A car travels a distance of 12 meters in 4 seconds. What is its average velocity during this trip?

Slide 32

Question 2 Is mass scalar or vector? No direction to mass! Its scalar!

Slide 33

Question 3 A rock is sitting on top of a cliff with 30 Joules of gravitational potential energy (GPE). The rock then falls off the cliff and hits the ground. As it hits the ground, how much KE does the rock have in Joules? SWBAT solve conservation of Energy Problems Energy is conserved. So, the energy in the beginning, equals the energy at the end! 30 in the beginning, means 30 at the end!

Slide 34

Question 4 If a 7 Newton force is applied over 2 meters, how much work is done? SWBAT solve conservation of Energy Problems

Slide 35

Question 5 A boy tugs a sled with a string. He pulls it with a 15 N force for a distance of 6 meters. The string is at a 25 0 degree above the horizontal and sled slides along the flat ground.

Slide 36

Question 6 A person holds a 8 kg box above his head by applying a 6 N force as he walks down the street a distance of 12 meters. How much work does the person do on the box? Force Distance

Slide 37

Question 7 A car is traveling at 5 meters per second. The car then accelerates at a rate of 2 m/s 2 for 2 seconds. What is the cars final velocity?

Slide 38

Question 8 What is x is equal to? 35 meters x 42 0

Slide 39

Question 9 Paul wants to see if running lowers blood pressure. Paul has 10 friends run 1 mile everyday for a year and 10 friends not run for a year. All 20 participants eat the same exact diet and exercise the same amount besides the running. Afterwards, he measures their blood pressure. What is the independent variable in this experiment? Running

Slide 40

Question 10 Paul wants to see if running lowers blood pressure. Paul has 10 friends run 1 mile everyday for a year and 10 friends not run for a year. All 20 participants eat the same exact diet and exercise the same amount besides the running. Afterwards, he measures their blood pressure. What is a control variable in this experiment? Diet, exercise besides running

Slide 41

Question 11 Convert 10 meters per second into kilometers per second.

Slide 42

Question 12 Convert 45 days into hours.

Slide 43

Question 13 Convert 34 kilometers per hour into meters per second.

Slide 44

Question 14 Convert 34 centimeters per second into meters per hour.

Slide 45

Question 15 Larry walks 56 meters North and then 24 meters South, what is Larrys distance traveled?

Slide 46

Question 16 Gary walks 22 meters North and then 42 meters South, what is Garys displacement?

Slide 47

Question 17 A car constantly accelerates from rest to a speed of 84 meters per second in 4 seconds. What is the cars acceleration?

Slide 48

Question 18 A truck traveling at 34 m/s slams on its breaks and comes to rest in 4 seconds. During this 4 seconds, that truck travels 94 meters. What is the trucks acceleration during this period?

Slide 49

Question 19 A ball is thrown straight upwards. At its highest point, what is its velocity equal to?

Slide 50

Question 20 A ball is thrown straight upwards, at its highest point, what is its acceleration equal to? Acceleration due to gravity is constant = -9.81m/s 2

Slide 51

Question 21 A hockey puck is hit off of the edge of a cliff. As it leaves the cliff, it is moving exactly horizontally with a speed of 5 meters per second. Two seconds later it is falling through the air. At this moment, what is its horizontal speed equal to? Horizontal speed is constant. So = 5m/s

Slide 52

Question 22 A ball is dropped off a 34 meter bridge. When it hits the ground, what is its velocity equal to?

Slide 53

Question 23 I push against a wall with a force of 54 N and it doesnt move. What is the force against me provided by the wall? Newtons Third Law: Equal and Opposite, so 54N

Slide 54

Question 24 A 4 kg textbook sits on the floor. What is the normal force provided by the floor?

Slide 55

Question 25 A boat, sitting on the earth, has a mass of 65 kg. What is its weight?

Slide 56

Question 26 A person pulls on a book to the right with a force of 56 N, another person pulls the book to the left with a force of 86 N, what is the net force on the book?

Slide 57

Question 27 A vehicle has a mass of 54 kg. The vehicle accelerates at a rate of 12 m/s 2 for 3 s. What is the net force on the ball during acceleration?

Slide 58

Question 28 As a worker for Van Houtens moving company, you have to push some furniture around. You push on a table with a force of 400 N, but it doesnt move. What type of friction causes the table not to move? Static Friction! Remember, Static means Still

Slide 59

Question 29 Youre pushing on the table with a force of 25N when it doesnt move. Now, you push harder, with a force of 45N, but the table still doesnt move. What is the Frictional Force equal to at this time? 45 N If something isnt moving, that means the force are balanced. 45N

Slide 60

Question 30 Which is greater, kinetic friction or static friction? Static! Its harder to get something started, then to keep it moving!

Slide 61

Question 31 Which is greater, s or k ? s, which means static! Its harder to get something started, then to keep it moving!

Slide 62

Question 32 Your grandfather tells you to push a 25 kg microwave across the counter so he can heat up his Hot Pocket. If the coefficient of kinetic friction is.25 and the coefficient of static friction is.30, how hard do you have to push to get the couch to begin moving?

Slide 63

Question 33 You are pushing a 45kg wheelchair down the road with an acceleration of 4 m/s 2, in order to do this you are pushing with a force of 220 N. What is the coefficient of kinetic friction between the road and the wheelchair?

Slide 64

Question 34 A 25kg dog is launched out of a canon with a speed of 45 m/s. What is the dogs momentum equal to?

Slide 65

Question 35 A horse and buggy initially has 200 kg x m/s of momentum. It crashes into a McDonalds and comes to a complete stop. If the collision takes 1.25 seconds, what is the average force on the horse and buggy?

Slide 66

Question 36 A 3 kg dart is on a spring that is at ground level. The spring is compressed 0.65 meters and the ball is then shot up into the air. If the ball reaches a peak height of 9 meters, what is spring constant of the spring equal to?

Slide 67

Question 37 A ball is dropped off a bridge with a height of 56 meters. What will its speed be when it hits the ground?

Slide 68

Importantly Use the Study Guide to help you. Practice solving the problems on your own and then check your answers. USE THE BLOG www.phaphysics.wordpress.com USE THE DISCUSSION BOARD FOR HELP