In one type of solar energy system, sunlight heats the air within solar panels, which heats copper tubes filled with water. what type of energy is produced by this system?
a. geothermal energy
b. hydroelectric energy
c. electric energy
d. heat energy

What do radio waves and microwaves have in common? both are at the side of the spectrum that has the shortest wavelengths. both are at the side of the spectrum that has the lowest radiant energy. both are at the side of the spectrum that has the lowest frequency. both are found next to visible light on the electromagnetic spectrum.

Astone is dropped with no initial velocity from the top of a cliff and hits the ground a time of 3.9 s later. what is the height of the cliff, in units of meters? you may assume that air resistance is negligible. give the answer as a positive number question 15 a figure skater is rotating at a rate of 200 revolutions per minute. what is the angular speed, in units of rad/s? 200 o 20.9 12000 o 3.33

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid