Arock has a mass of 210g and occupies a volume of 70cm3 what is the density?

What was the first instrument to ever record an earthquake?

Atrain is traveling at 30.0 m/s relative to the ground in still air. the frequency of the note emitted by the train whistle is 262 hz. the speed of sound in air should be taken as 344 m/s. what frequency (f approach) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and approaching it? what frequency (f recede) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and receding from it?

Choose the correct general statement concerning the total potential and kinetic energy at any point along the arc of swing. the total energy at any point along the arc of swing of the pendulum is always less than 12 joules. the total energy at any point along the arc of swing of the pendulum is always more than 12 joules. the total energy at any point along the arc of swing of the pendulum is always equal to 12 joules. not enough information to determine