The Frost is on the Pumpkin

As the temperatures fall, start carrying around an extra jacket in your backpack. You are going to find that some classrooms will be like Antarctica and others will more resemble Death Valley. Make sure that you can vary your layers accordingly...

Honors Physics reviewed their impulse-momentum labs today and related the results to what we already know about applied and restoring forces of elastic materials. We then turned our attention to conservation of momentum and how Newton's Third of Motion and the impulse-momentum theorem lead to the conservation of momentum in systems. I haven't had a chance to update the course website lately, so I'll put a link to the momentum chapter solutions here so that you can check your work from home. Tomorrow, we'll go over the homework problems and then toss a look back to energy and track the conservation (or lack thereof) of kinetic energy in collisions.

Physical Science B and E reviewed Archimedes Principle and then spent time practicing the mathematical applications of buoyancy. Your homework problems should, like all word problems, thought of as puzzles or mysteries. How do you take what you are given and expected to know and use it to find the answer? Try one technique and if that leads nowhere, try something else. Things to remember when working buoyancy problems:

• The volume of the object is equal to the volume of the displaced fluid.


• The mass of the object and the displaced fluid must be in kilograms in order to calculate weight in Newtons


• The density formula can be used to calculate mass, volume or density of either the object or the displaced fluid. Consider how to use this formula with the information given in the problem to help you along towards the solution.

The answers for your homework problems:

1. F_g = 2.7 x 10⁵ N; F_b = 4.4 x 10⁸ N; object floats


2. F_g = 1.82 N; F_b = 0.15 N; object sinks


3. F_g = 73 N; F_b = 2.2 x 10³ N; object floats; density = 0.17 kg/m³


4. F_g = 11.8 N; F_b = 4.6 N; object sinks; density = 11 g/cm³

Physics F discussed conservation of momentum and how this principle can be used to analyze motion in multi-body systems. Keep in mind that the total momentum of a systems is conserved, but the momentum of individual objects in the system will change after the collision. We related Newton's 3^rd Law of Motion and the impulse-momentum theorem to explain why conservation of momentum holds true and the pattern of momentum change in collisions. Tomorrow's lab will let you analyze momentum and impulse in more detail.

Physics G conducted a lab that concentrated on the impulse-momentum theorem. The agreement between the impulse delivered on an object and the object's momentum change was tested, as was the effect of elasticity on the impulse delivered by a material. We will go over this lab tomorrow and then take on the concept of conservation of momentum.

Homework

Honors Physics A: Practice 6D and 6.2 SR #2,4
Physical Science B and E: Archimedes' Principle problem sheet
Physics F: Read lab protocol sheet
Physics G: Complete lab write up