# HP Cycle 15

## 12/2 - 12/7

F 12/2

M 12/5

T 12/6

W 12/7

### 🟢 5: F 12/2, 🔵 7: M 12/5 - pulley problems

Today, we'll look at what a pulley does... basically it changes the direction of the force. Here, we'll start looking at Newton's 2nd Law problems with more than one object in the system. We'll have to write a ΣF statement for each object as well as the total system. Then, we'll work on page 5 of Big Newton's Law Packet. (SOLUTIONS to whole packet)

We'll then solve "table top pulley problems" with #1-2 in Table Top Pulley Problems, Solutions #1-2.

Optional Challenge Problems: Two Block Problems #1, 2, and 4. SOLUTIONS

Homework: Finish #1-2 in Table Top Pulley Problems, Solutions #1-2 and upload to ✏️ Google Classroom by Tuesday, December 6th at 10pm. If you need support, watch the videos below (repost):

### 🟩 5: M 12/5, 🟦 7: T 12/6 - 📖 system & pulley problems

Today, in order to reinforce the problem-solving techniques for multiple objects in a system, we'll work on Chapter 5 textbook problems in 📖Mastering Physics "Ch 5.5 - multiple mass systems": #42, 44, 46, (47 assigned mistakenly), 79, 82, 84.

Optional Challenge Problems: Two Block Problems #1, 2, and 4. SOLUTIONS

Homework: Finish 📖Mastering Physics "Ch 5.5 - multiple mass systems" by Wednesday, December 7th at 10pm. Assessment of all of Newton's Laws in 1-D Friday, December 9th.

### 💚 5: W 12/7 - adding vectors

Today, we'll see how we can add vectors that are not at right angles to each other. We will learn to break vectors into x- and y- components and why that is useful to us. We'll try this example problem together:

Homework: Assessment of all of Newton's Laws Friday, December 9th. If you'd like to review more on vector addition, you can watch these videos:

For the example in the next video, imagine that two people are pulling on an object placed at the origin. The red person pulls with a force of 6.32N at an angle of 18.4 degree, while the blue person pulls with a force of 5.66N at 45 degrees.

The goal is to find the resultant force. In other words, instead of two people pulling in different directions, if there were one strong person who could exactly replicate the net force on the object, with what magnitude and direction of force would the strong person exert on the object to get the exact same result? Start this problem by first drawing a picture and by then finding the x- and y-components of each of the force vectors. Then watch the video below.

### 💙 7: W 12/7 - Newton's Laws review

Today, we'll spend the period reviewing for your upcoming exam on Newton's Laws in one dimension. Review your submitted classwork problems, or do additional textbook problems or any of the optional problems from this unit. Remember that you will have two options on the exam:

• Option 1 (comprehension) problems will come from any of the required classwork problem sets and will earn a maximum of 80%.

• Option 2 (application) problems will be new problems that you've never seen before.

Both of these options are designed to be roughly the same difficulty level; the only difference is that you've seen the Option 1 problems before. My recommendation with these two options is that you should read the option 2 problem first. Then, if you decided it's too difficult, then do the option 1 problem. If having the two options is too stressful for you, then just plan on doing all option 2 problems.

There will be three free response questions for which you will be able to choose from Option 1 or Option 2. The directions will be written at the beginning of each problem, but for your advanced review, I have reproduced them here:

Make sure to draw free-body diagrams of ALL objects, show your choice of coordinate system, write ΣF statements, show all algebra with variables, and solve! Only plug in numbers in the last step of every problem. Units on ALL numbers. You may use either g = 9.8m/s2 or g = 9.81m/s2. You may use the same single free body diagram throughout a particular problem if appropriate. Three sig figs in all of your answers please. Write your answer with units on the line after the question.

Optional Challenge Problems: Two Block Problems #1, 2, and 4. SOLUTIONS

Homework: Assessment of all of Newton's Laws next class - Friday, December 9th.