DAY 46

Happy Pi Day

RIP Stephen Hawking

#Goals: SWBAT...

1. Define momentum

2. Solve basic momentum problems.

3. Create a table of friends

WARM-UP & HW Check:

A. What is the meaning of Δv? What about Δt? Δp?

B. Imagine a Big Rig hits a Prius. Who wins? Does the velocity of the Prius and/or Big Rig matter? Does the mass of the Prius and/or Big Rig matter?

C. Imagine that when they impact, the Big Rig is going North at 50mph, and the Prius is going South at 50mph. The two vehicles stick together after the collision. Which way will the stuck vehicles travel? Are you sure? How can you be so sure???

D. If you haven't yet, find the formula and definition for Momentum

CLASSWORK:

#046A: Momentum Notes

• "Going into the all-star break, the Lakers are gaining momentum!" What does that mean? Think-Pair-Share
• Momentum Definition: mass in motion
• Symbol: p
• Equation: Momentum = mass • velocity
• Vector? YES

Example: Consider a 0.5-kg physics cart loaded with one 0.5-kg brick and moving with a speed of 2.0 m/s. The total mass of loaded cart is 1.0 kg and its momentum is 2.0 kg•m/s. If the cart was instead loaded with three 0.5-kg bricks, then the total mass of the loaded cart would be 2.0 kg and its momentum would be 4.0 kg•m/s. A doubling of the mass results in a doubling of the momentum.

What is the relationship between mass and momentum? Direct (linear) or inverse?

Basic Practice Problems

1. Your brother’s mass is 35.6 kg, and he has a 1.3-kg skateboard. What is the combined momentum of your brother and his skateboard if they are moving at 9.50 m/s?
2. Determine the momentum of a ...
3. a. 60-kg halfback moving eastward at 9 m/s.
4. b. 1000-kg car moving northward at 20 m/s.
5. c. 40-kg freshman moving southward at 2 m/s.
   1. A car possesses 20 000 units of momentum. What would be the car's new momentum if ...
   2. a. its velocity was doubled.
   3. b. its velocity was tripled.
   4. c. its mass was doubled (by adding more passengers and a greater load)
   5. d. both its velocity was doubled and its mass was doubled.

#046B: Table of Friends

• Today, you will make a Table of Friends. This is an equation sheet which you can use on any quiz or exam. It can only have (at max) symbol, equation, units, quantity measured, key words.
• You should bring it to class everyday, as we will add to it
• LINK

PERIOD 6: FIRE EXTINGUISHER

Learning at home

• Complete your Table of Friends (#046B) for credit.
• Make sure to add Work and Energy information to your Table

IMPULSE-MOMENTUM THEORY

https://www.youtube.com/watch?v=fdeH6Ksedwk

Impulse is the change in momentum (Δp).

A. Is the impulse when the brick hits the table the same or different as the brick hitting the foam?

When our video presenter jumps from the table, he begins falling.

B. Does his momentum increase, remain constant, or decrease?

C. Does he want to experience a strong force when he lands? Why/why not?

D. How does he protect himself upon landing?

E. Why are running shoes helpful for our feet?

Impulse Notes:

What does it look like when a force is applied to an object?

http://scienceblogs.com/startswithabang/2012/09/15/weekend-diversion-the-physics-of-happy-gilmore/

https://ssl.wsu.edu/wp-content/uploads/sites/510/2015/01/Bat-Ball-Impact-Bat-Ball-Science-Fig-4.1.jpg

https://www.asme.org/engineering-topics/articles/applied-mechanics/engineering-our-favorite-pastime

ADD THE NEXT 4 LINES TO YOUR Notes

Formula: FΔt

Def: product of the average force and the time interval of the collision.

Units: Newton-seconds

Symbol: none

Video: https://www.youtube.com/watch?v=ph48Xwj_eS8

Try the problem from the video

Notes:

F=ma

F=mΔv/t

F-t=mΔv (Impulse-Momentum Theorem)

3. Two Types of Collisions (add to your notes)

• Elastic collision. In an elastic collision, the total kinetic energy (energy from movement) in the system is the same before and after the collision. If losses to heat and deformation are much smaller than the other energies involved, such as when two pool balls collide and go their separate ways, you can generally ignore the losses and say that kinetic energy was conserved.
• Inelastic collision. In an inelastic collision, the collision changes the total kinetic energy in a closed system. In this case, friction, deformation, or some other process transforms the kinetic energy. If you can observe appreciable energy losses due to nonconservative forces (such as friction), kinetic energy isn’t conserved.

4.