Answer: Solution: (1) ab slides down to cut the magnetic field lines. The direction of the induced current generated is perpendicular to the paper and points to the reader. The force is as shown in the figure. It is affected by gravity mg, support force N, The effects of the four forces of friction force f and ampere force F; as the speed increases, the induced current increases and the ampere force gradually increases, while the combined external force gradually decreases, and the acceleration gradually decreases. Therefore, rod ab performs an accelerating motion with an initial velocity of zero and gradually decreasing acceleration. When the acceleration is zero, the speed is maximum, and finally it performs a uniform linear motion
(2) Assume that when the speed of the rod is v, the induced electromotive force is E, and the current in the circuit is I, then E=Blv I=ER F=BIl
Then we get: F=B2l2vR
According to Newton's second law, we get: mgsinα-F -μmgcosα=ma
The solution is: a=g (sinα-μcosα)-B2l2vmR
When the acceleration is zero, the speed is maximum, set to νm,
The solution is: νm=mgR(sinα?μcosα)B2l2.
Answer: (1) Analyze the motion properties of rod ab during its sliding process as shown above, and draw its force diagram as shown above.
(2) The maximum speed of the ab rod is mgR(sinα?μcosα)B2l2.