May I have a 50V, 3A DC motor with IRF540?
If you power the 50 V motor with a 50 V supply, then when the FET is OFF, it will drop that full 50 V. The max Vds for the IRF540 is 100 V.
How is the schematic?
Like all N-Channel designs, you will use it as a low-side switch.
Need heat dissipation?
Probably. I discussed how to determine that in the video.
It will depend on what voltage you use for Vgs since that controls the Rds.