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🟢 8: F 11/14 - 📖 friction problems
🟢 8: F 11/14 - 📖 friction problems
Today, we'll first recap with this Friction Presentation. If you did not watch the friction video, watch that first. Then, we'll work on on friction problems collaboratively. Optionally work on problems from Chapter 5 in your 📖textbook: #27, 29, 31, 32, 71, 73.
Optional Extra Practice: in addition to the problems above, you may try #11-17 on page 2 of Big Newton's Law Packet. SOLUTIONS to pp 1-2 of Packet.
Homework: Optionally complete textbook problems above.
🟩❗8: M 11/17 - vectors at angles
🟩❗8: M 11/17 - vectors at angles
Today, we'll learn about vectors that are at angles. We'll see how to add two vectors that are perpendicular to get a diagonal "resultant" vector. We'll learn to resolve diagonal vectors in x- and y-components using trigonometry (SOH CAH TOA). Finally, we'll begin to explore how we can use Newton's 2nd Law with diagonal vectors.
Presentation:
Homework: If you'd like to review more on vector addition, you can watch these videos:
💚 8: T 11/11 - 📓 static equilibrium lab
💚 8: T 11/11 - 📓 static equilibrium lab
Today, we'll look at "static equilibrium" problems - where the forces are balanced. We approach static equilibrium problems by making ΣFx=0 and ΣFy=0, but some of the forces will be at angles.
We'll start by learning about a problem that rock climbers encounter when building an anchor. We'll learn the physics theory and engineering behind climbing safety. In order to fully understand the problem, we'll look at how Newton's Second Law acts in two dimensions with a physical model of the situation. We'll investigate how the angles at which the slings hang can impact the amount of force they experience and can support. We'll perform a lab where we try to find the mass of a mystery object using two dimensional forces.
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 a free body diagrams of the knot. Record the two angles and two tensions for the situation at your lab table. Calculate the mass of the mystery object. Mass the mystery object on the digital balance, and do a percent error calculation.
If you have any trouble understanding the calculations for the lab, check out the following video. 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.)
Homework: If you'd like to get ahead, check out the 📖 textbook problems in the next post. Quiz on static equilibrium & 2-D vector forces on Friday, November 21st.
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