The SI unit of mechanical power is:

1. Joule
2. Watt
3. Newton-second
4. Joule-second

Watt is the unit of power (symbol is W). It is named after James Watt, the inventor of the steam engine. One watt is defined as the energy consumption rate of one joule per second.

1 W = 1 J / 1 s

It has dimensions of [ML2T-3]

The correct option is B.