The power output of an engine is 3 kW. How much work does the engine do in 20 s?

Here given, the power output of the engine $P=3\ kW$

Time $t=20\ s$

So, work done by the engine $=Power\times time$

$=3\ kW\times 20\ s$

$=60\ kJ$

Thus, the work done by the engine is $60\ kilo-Joule$.