Aboy yells in a narrow valley. the sound reflects off of a boulder that is 80m away. how long will it take to hear the echo if the speed of a sound wave is 320 m/s

When someone slams her books on a table the kinect energy is transferred into vibrations that travel to your ears as sound waves which statement describes the movement of those waves

How would a small bar magnet be oriented when placed at position x?

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?