DAY 85
Goals: SWBAT...
1. To prove that momentum is, or is not, conserved
2. To solve momentum problems
Warm-Up (5min):
A clown is on the ice rink with a large medicine ball. If the clown throws the ball forward, then he is set into backwards motion with the same momentum as the ball's forward momentum. What would happen to the clown if he goes through the motion of throwing the ball without actually letting go of it? Explain.
Dale, Mel, and Shanelle are astronauts outside a spaceship. They each have the same mass and the same strength. Dale and Mel decide to play catch with Shanelle, intending to throw her back and forth between them. The game begins when Dale throws Shanelle to Mel. Describe the motion of Dale, Mel and Shanelle as the game continues. If we assume that each throw involves the same amount of push, then how many throws will the game last? (note: there is a numerical answer to this question. Pick a velocity for the first throw, and think about how that would change for Shanelle as she gets thrown)
answers to the warm-up are at the very bottom of this page
CLASSWORK
1. #085A: Conservation of Momentum Notes
- Take notes on everything in RED, including black tables below red headings (like the money conservation example)
LINK: https://www.physicsclassroom.com/class/momentum/Lesson-2/Momentum-Conservation-Principle
2. #085B: Momentum Conservation Practice Problems
When fighting fires, a firefighter must use great caution to hold a hose that emits large amounts of water at high speeds. Why would such a task be difficult?
A large truck and a Volkswagen have a head-on collision.
a. Which vehicle experiences the greatest force of impact?
b. Which vehicle experiences the greatest impulse?
c. Which vehicle experiences the greatest momentum change?
d. Which vehicle experiences the greatest acceleration?
If a ball is projected upward from the ground with ten units of momentum, what is the momentum of recoil of the Earth? ____________ Do we feel this? Explain.
If a 5-kg bowling ball is projected upward with a velocity of 2.0 m/s, then what is the recoil velocity of the Earth (mass = 6.0 x 1024 kg).
A 120 kg lineman moving west at 2 m/s tackles an 80 kg football fullback moving east at 8 m/s. After the collision, both players move east at 2 m/s. Draw a vector diagram in which the before- and after-collision momenta of each player is represented by a momentum vector. Label the magnitude of each momentum vector.
In an effort to exact the most severe capital punishment upon a rather unpopular prisoner, the execution team at the Dark Ages Penitentiary search for a bullet that is ten times as massive as the rifle itself. What type of individual would want to fire a rifle that holds a bullet that is ten times more massive than the rifle? Explain.
A baseball player holds a bat loosely and bunts a ball. Express your understanding of momentum conservation by filling in the tables below.
3. 085C: Review for tomorrow
Learning at Home/HW
- Complete the CW from today
Goals: SWBAT...
1. Momentum - Is It Conserved?
2. To observe patterns in a collision between two objects, and to develop a rule for predicting the post-collision velocity of the two objects.
Warm-Up (5min):
Golf. When a golf club hits a golf ball, which experiences a larger force, club or ball?
Pool. When a cue ball hits the 8-ball, which experiences a larger force cue ball or 8 ball?
Figure Skating: Consider the interaction between a male and female figure skater in pair figure skating. A woman (m = 45 kg) is kneeling on the shoulders of a man (m = 70 kg); the pair is moving along the ice at 1.5 m/s. The man gracefully tosses the woman forward through the air and onto the ice. The woman receives the forward force and the man receives a backward force. Which force is larger? Who experiences a larger velocity change?
CLASSWORK
085A: Fish Catch Interactive
Copy, then complete the sentence. Before the collision, only one of two objects is moving. All the momentum of the system resides in a single object before the collision. After the collision, both objects move together at the same _______ as if they were a single ________.
In this activity, you will attempt to develop a mathematical rule for predicting the postcollision velocity for any collision that possesses this characteristic. You will attempt to develop the rule in the form of an equation that states the post-collision velocity (vf) as a function of the pre-collision velocity (vi) and the masses of the moving (m1) and the stationary (m2) objects.
Instructions/Handout Link: https://www.physicsclassroom.com/getattachment/Physics-Interactives/Momentum-and-Collisions/Fish-Catch/Fish-Catch-Exercise/FischCatchActivity.pdf?ext=.pdf
Copy the data table into your notes, then use the interactive to collect data. Once you have all the data, create a rule (equation) relating the qualities described in the paragraph above.
Interactive Link: https://www.physicsclassroom.com/Physics-Interactives/Momentum-and-Collisions/Fish-Catch/Fish-Catch-Interactive
Learning at Home/HW
085A: Complete the Classwork
085B: In honor of my 40th birthday (which is tmw, Wednesday), how about we got 100% homework completion? :-D
In case you're wondering, I like cans of Coke, and Chik-fil-a gift cards.
Watch the following, take notes, and answer the Edpuzzle questions so you can be ready for Wednesday. Enjoy the Nerd-A-Pult
Edpuzzle Video: https://edpuzzle.com/media/588649e2fc574b49613432dc
WARM-UP
Draw the following three images (1-3), and state which way the BOLD particle(s) would move
1) (+) (-) (+)
2) (+) (-) (+)
3) (+)(+) (-)
CLASSWORK
085A: HW Review
085B: Electric Field Hockey Interactive Sim
On your handout, draw the following:
starting location of the puck
goal
location/sign of all charges
path of puck
electric field lines
HOMEWORK
Still struggling with Coulomb's Law? Here's some help: Video LINK
1. If you didn't finish it in class, complete 085B
2. Complete Friction Rod Activity from last week. Due Friday
WARM UP ANSWERS
1. Stay in the same place. The act of throwing would push you backwards to conserve momentum, and holding onto the ball would then cause you to move forwards, returning to the starting point.
2. Including the first throw, the game would last two throws. Mel can't throw Shanelle hard enough for her to catch up to Dale.