Monday This week, we review a little and also study the final topic: How torque is the rate of change of angular momentum, and how they are both vectors, so when torque is perpendicular to angular momentum, torque doesn't increase or decrease angular momentum. Instead, torque causes the angular momentum to change direction. This is precession. Before Class

Grading and Project #2: Hi everyone. Because there is no project #2, Your grades will be determined on a 95% total scale, essentially raising the total grade by a factor of 1.05.

I've posted solutions to MT#2 on the main class website. Please read through the solutions, even if you aced the exam. In particular, I show you a nice way to solve the first problem very quickly that I think is worth seeing, and no one got the carousel problem perfectly, so please read through them.

Check out the feedback from last Wednesday, posted on main class website.

PS#9, due next Monday, posted on main class website.

Finish PS#8 hand in today in class.

See solutions for PS#7 posted on main class website.

Big Exam #6 indicates that we have important fundamental misunderstandings of angular momentum, besides not recognizing that angular momentum of a point mass about an external point = linear momentumximpactparameter:

- There is a common student misconception that momentum and angular momentum are the same thing or convertible to each other, just like linear kinetic energy and rotational kinetic energy are both kinetic energy. This is not true. Please check units right of these four things and notice that momentum isn't angular momentum. - Just as force and torque are different quantities with different units. Notice that force can exert a torque about a center of rotation only if it is connected to the center of rotation with a perpendicular radius, or partly perpendicular radius. Similarly, a body with momentum can have angular momentum about a center of rotation if there is a nonzero impact parameter.

I ask that you again watch the video on youtube without the questions describing angular momentum of a point mass. Then, please do the last problem on the problem set, which is your BE!#6. Maybe in class Monday, you can tell me what I might have changed to make this video more effective. Please count on seeing this kind of problem in your future.

During Class

Tuesday Angular Momentum as Stability - Angular Momentum is a Vector!

MondayThis week, we review a little and also study the final topic: How torque is the rate of change of angular momentum, and how they are both vectors, so when torque is perpendicular to angular momentum, torque doesn't increase or decrease angular momentum. Instead, torque causes the angular momentum to change direction. This is precession.

Before ClassVeritassium Which Block Goes Higher?indicates that we have important fundamental misunderstandings of angular momentum, besides not recognizing thatBig Exam #6of a point mass about an external point =angular momentumlinear momentumximpactparameter:- There is a common student misconception that momentum and angular momentum are the same thing or convertible to each other, just like linear kinetic energy and rotational kinetic energy are both kinetic energy. This is not true. Please check units right of these four things and notice that momentum isn't angular momentum.

- Just as force and torque are different quantities with different units. Notice that force

exert a torque about a center of rotation only if it is connected to the center of rotation with a perpendicular radius, or partly perpendicular radius. Similarly, a body with momentumcanhave angular momentum about a center of rotation if there is a nonzero impact parameter.canI ask that you again watch the video on youtube without the questions describing angular momentum of a point mass. Then, please do the last problem on the problem set, which is your BE!#6. Maybe in class Monday, you can tell me what I might have changed to make this video more effective. Please count on seeing this kind of problem in your future.

During ClassAngular Momentum as Stability - Angular Momentum is a Vector!TuesdayBefore ClassDuring ClassPrecessionWednesday:Before ClassIn ClassAfter ClassThursday:During Class