tag:blogger.com,1999:blog-5088860151651047897.post4055604765082694696..comments2024-03-25T10:56:59.380-04:00Comments on Jacobs Physics: Mail Time: Is Pluto's Angular Momentum About the Sun Conserved?Greg Jacobshttp://www.blogger.com/profile/03854009948036330746noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-5088860151651047897.post-57550672217480274462018-02-25T16:03:07.490-05:002018-02-25T16:03:07.490-05:00I think the confusion comes from incompletely diag...I think the confusion comes from incompletely diagramming it. Draw the ellipse, with the sun at one focus, and the foci on a horizontal line. Put Pluto at a point that is at, say, "noon" if this were an elliptical clock. Draw a vector showing the tangential velocity of Pluto, and a vector representing the gravitational force exerted on Pluto by the sun. Note that the angle is not 90 degrees. This means there is a tangential component to the force being applied to Pluto. Of course, your answer is still correct; the gravitational force is parallel to the lever arm (which is what our drawing has forgotten), which is what matters here. But I've found that's where the confusion comes from; people take that angle I mentioned to be the "theta" of Torque = F l sin(theta), which basically is confusing this situation with any number of circular-motion situations in which a tangential component of a force would indeed be applying torque to the system.Willnoreply@blogger.com