# HP Cycle 13

## 11/17 - 11/22 F 11/17 M 11/20 T 11/21 W 11/22
half day

### 🟢 5: F 11/17 - 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: HomeworkAssessment of all of Newton's Laws Monday, November 20th.  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.

### 🟩❗ 5: M 11/20 - Newton's Laws 1-D Assessment

Newton's Laws 1-D Assessment Today!

After the assessment, I will introduce the lab for next period so that you can start setting it up in your lab notebook.  If there's time remaining, watch the 8-minute lab video in the next post.

Homework:  Make sure you review vector addition so that you are prepared for the lab next period.  Finish watching the 8-minute lab video so that you can finish the lab in the shortened period.

### 💚 5: W 11/22* - 📓 static equilibrium lab Today, we'll look at "static equilibrium" problems - where the forces are balanced.  We'll look at how Newton's Second Law acts in two dimensions by performing a lab where we try to find the mass of a mystery object using two dimensional forces.  See the figure for set-up of the "y-tension problem."  In these types of problems, we'll look at making ΣFx=0 and ΣFy=0, but some of the forces will be at angles.

You will set up three asymmetrical situation with the Y-tension string.  Assume the string is ideal (massless and inelastic).  Use a protractor to measure the angle of each string with the horizontal.  Use the spring scales to measure the tension in each string. In your lab notebook, draw three free body diagrams of the knot.  Record the two angles and two tensions for each of the three situations.  For each of the three situations, calculate the mass of the mystery object.  Average the three experimental values.  Mass the mystery object on the digital balance, and do a percent error calculation.

If you have any trouble understanding the calculations here, check out the following video below.  The strategy is to draw a free body diagram of the knot.  (If the knot is made out of ideal or massless string, it does not have a force of gravity on it.)

HomeworkNone.  🦃🍗 Happy Thanksgiving! 🍗🦃

Today's lab is due in class next Tuesday, but you should have been able to finish most of it during this period.  (If you'd like to get ahead, check out the 📖 Mastering Physics problems in the next post.)