A, B, and C are vertices of a moving rigid equilateral triangle. At a particular instant, A moves with velocity u along AB towards B. C moves away from B along BC with an unknown speed. Find the velocity of B.
00:36 Hint given | 02:28 Solution starts | 06:47 Answer
Question R2L2: Concepts used in solution
Moment of inertia | Dimension analysis | Torque | Angular impulse
Problem statement
A uniform square plate is placed on a rough horizontal floor hinged at one corner. When it is given an angular velocity w about a vertical axis through this corner, as shown in figure(a), it takes time t to come to a complete stop. Now the same square plate is hinged about the center and given the same angular velocity about a vertical axis as shown in figure(b). How long will it take to come to a complete stop now?
Using just parallel axis theorem and scaling argument, find the moment of inertia of a thin stick about an axis passing through its center and perpendicular to its length. On what other shapes can this idea be used?
00:41 Hint given |01:50 Solution starts | 07:20 Answer
Question R3L2: Concepts used in solution
L due to translation and rotation | Vector cross product | Right hand rule for L |
Derivation of L formula shared by MIT can be found here
MIT OCW video on Angular Momentum of Translation and Rotation
Problem statement
A disc of radius R and mass M rolls without slipping in the direction of the positive x-axis with speed u. Are there points about which the angular momentum of the disc is zero?
Fun with Physics Problems 