Here are the pics and screenshots with captions from last week:

PhySP18SS6.7.1: Add your pics to the wall!

PhySP18SS6.7.2: Ultimate fighting Tool used to solve a free fall problem. The mark of a great question is that it reduced down to other lesser equations (like the 3rd Blue)

PhySP18SS6.7.4: 6.15.12 Using UFT to solve a problem

PhySP18SS6.7.5: A very famous graph in Physics. E = K + U which means Total Mechanical Energy = Kinetic Energy plus Potential Energy. And . . . the Total Mechanical Energy (E) is conserved which means you can’t lose any or gain any in a closed system.

PhySP18SS6.7.6: The difference between dot products and cross products. Pretty much everything you do all day is a series of dot products and cross products. Anything involving changing energy is a dot product of two vectors and anytime there is any rotation it is a crossproduct. Heck, if there is light anywhere around you it is the combination of two dot products and two cross products.

PhySP18SS6.7.7: THe Natural Balance Point is pretty much what it sounds like it is. It is the point that gravity recognizes. As far as gravity is concerned ALL the mass of the object is at the NBP. The NBP has an equal mass distribution radially (called the moment of Inertia (I).

PhySP18SS6.7.8: Torque is the only type of cross product we use, but there are many more.

PhySP18SS6.7.9: 3D torque. Sometimes I forget how awesome torque is.

PhySP18SS6.7.10: Messing around with torque in general. This doesn’t go to a particular problem. We jsut made this one up. It is a static problem so it can’t move in any direction OR rotate.

PhySP18SS6.7.11: We made this one up too.

PhySP18SS6.7.12: yep, made it up

PhySP18SS6.7.13: This is from Sheet 6.16.1 Only 1st hour did this one.

PhySP18SS6.7.15: 6.16.2

PhySP18SS6.7.16: 6.16.3

PhySP18SS6.7.17: THT6B.12 the second one with Levi and Daniel and all that crazy organic manure.

PhySP18SS6.7.18: 6.16.5 which also helps you with THT6B.15

PhySP18SS6.7.19: 6.16.6

PhySP18SS6.7.21: THT6B.14 It’s fine if you just want to think of phi as the reference angle, but just so you know it is actually the obtuse angle that extends from the LOA all the way around to radial pointer vector. This has to be the case because Torque has to be negative for this situation since it is causing clockwise motion. All clockwise rotation is negative. So . . . since torque = |r| |F| sin (phi) phi must be in the 3rd or fourth quadrant for sin (phi) to be negative. If that didn’t make sense, don’t worry, it’s too late in the year to worry about it.

PhySP18SS6.7.23: THT6B.14

PhySP18SS6.7.24: The fishing pole one. 6.16.7

PhySP18SS6.7.25: The Matrix version of the cross product solution. This looks hard, but turns out to be laughably easy..

PhySP18SS6.7.26: 6.16.10 This is the reason WHY it becomes so easy. As long as you can get a column of your 3 x 3 matrix a column of zeros, your life is easy. This will be the case for your test next week.

PhySP18SS6.7.27: more torque stuff

PhySP18SS6.7.28: more torque stuff

PhySP18SS6.7.29: more torque stuff

PhySP18SS6.7.30: We used to have a torque building contest where you had to have to make a mobile which has at least four different torque and hang it from the ceiling. What happened to all those?