Which is heavier-warm air or cold air?

Can any one Explain how energy is conserved in a heat pump.

How many top quark lifetimes have there been in the history of the universe (i. e., what is the age of the universe divided by the lifetime of a top quark) ? note that these powers of 10 follow the same rules that any exponents would follow?

In the broadest sense, what was the kinectic molecular theory designed to explain?

Which property of an atom's structure was used to organize the periodic table? A. outermost electron B. total electrons C. total protons D. outermost protons

Which of the following questions would be answered using concepts from physics? A. What are the forces that cause a pendulum to swing? B. How does rust form from iron and water? C.

The train traveled 500 kilometers north to Odessa in 2 hours. What's the train's speed? What is the velocity?

Are microwaves and radio waves faster or slower than other types of electromagnetic energy?

If you dive under-water, you notice an uncomfortable pressure on your eardrums due to the increased pressure. The human eardrum has an area of about 70 mm2 (7*10-5m2), and it can sustain a force of about 7 N without rupturing.

Why cant kinetic energy ever be greater than potential energy

For a stationary observer, when the source of a sound is moving, its pitch appears to change.