Why do black holes happen?

What is the method of adding crests and troughs of interfering waves together to describe a new wave?

The force that pulls the tides

Substance can undergo physical change or chemical change? What is difference between these two kinds of changes?

Describe the three main ideas of Dalton's atomic theory in your own words.

Which diagram below best represents the magnetic field near a bar magnet?

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.