the distance from sevenoaks to penzance by rail is 420 km. At what average speed must a train travel to over this distance in 4 hours ?

If a clock aboard a space ship traveling at 0.900 c of the speed of light relative to earth chimes once at the beginning of the hour and again when it reads one hour later, how much time would an observer on earth say elapsed between the two chimes?

True or false: the cycle of seasons on the earth is caused by the tilt of the earth on its axis toward and away from the sun.

A40.0 l tank of ammonia has a pressure of 12.7 kpa. calculate the. volume of the ammonia if it’s pressure is changed to 8.4 kpa while its temperature remains constant.