Q. Four identical masses of mass 900kg each are placed at the corners of a square whose side lengths are 10cm. what is the magnitude of the net gravitational force on one of the masses, due to the other three?
Q. Mr. Physics drops a rock down a 250-meter deep well. Upon impact with the bottom of the well a short burst of sound is produced with a frequency of 250 Hz. How long after he drops the rock does he hear it hit the bottom of the well?