Recent content by cler

no, of course, it is the same, but i needed to know why the angular momentum term vanished and i needed kind of a mathematical proof. that's all. i just understood while asking you. thank you

i understand now. Even using polar coordinates when the particles stop l=0 and since l is a conserved quantity the term l2/(2mr2) will vanish. This will also mean that r and v are parallel at all times, l=m(r x v) Thank you very much for your time and help

Sorry, perhaps i didn't explain myself properly. The radius of the circular orbit is known. When the motion is stopped why don't you need polar coordinates. I mean will the particles go in straight line toward each other. or will the reduced mass particle describe a straight line toward the...

Ok, but if i use polar coordinates the velocity can be decomposed in a radial and angular component. So then appears the term with l (angular momentum) which is constant in this central forces case. why can't i calculate the time to collide using that radial velocity?

Homework Statement Two particles moving under the influence of their mutual gravitatonial force describe circular orbits about one another with period τ.if they are suddenly stopped in their orbits and allowed to gravitate toward each other. show that they will collide in a time τ/4√2...

Homework Statement A pendulum consists of a uniform rod of mass m and length l hanging from the bottom end of a light rod of length l which top end is fixed to the ceiling. (see file attached) System moves in a vertical plane. Find equations of motion. Coordinates of the center of mass...

Ok, now i get it. Thank you very much!

Ok, but basically what i do is saying that the energy at the beginning Ei is potential energy due to gravity. Then when the rod hits the table potential energy equals zero, so i only have kinetic energy which is a sum of translational and rotational energy. which is the translation of the center...

Homework Statement A uniform thin rod of mass m and length l is standing upright on a table, then given a tiny kick so it tips over. The lower end is fixed. Find angular velocity when it hits the table. Homework Equations The Attempt at a Solution So I applied conservation of...