Solar energy is free and renewable.
Its efficiency is determined by the photovoltaic or heat-exchanging equipment used, and the efficiency of the infrastructure built to interconnect them. None of that depends on the time of the year. For a given amount of solar energy absorbed by the collector, the amount of useful output energy doesn't change with the season.
use consevation of linear momentum
- m1v1+m2v2=(M1+M2)V3
- 281(2.82)+209(-1.72)=(209+281)V2
- 792.42-359.48=490v3
- 432.9=490v3
- V3=0.88m/s