Select all the correct answers. Which two statements describe challenges faced by renewable energy sources?
Geothermal energy requires a great deal of land.
Development of wind energy is a threat to bats and birds.
Toxic chemicals are used in the manufacture of solar cells.
Most renewable energy sources produce greenhouse gas emissions.
Hydropower development has no impact on wildlife.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2