Astudent on the ground observes the sun just as it sets. his friend, who is located 100 meters higher up in a tall building, tells him via cell phone that she observes the sun setting 77 seconds after he does. assuming that the path of the setting sun is perpendicular to the horizon, use this information to estimate the radius of the earth.

A75-hp (shaft output) motor that has an efficiency of 91.0 percent is worn out and is to be replaced by a high-efficiency motor that has an efficiency of 95.4 percent. the motor operates 4368 hours a year at a load factor of 0.75. taking the cost of electricity to be $0.12/kwh, determine the amount of energy and money saved as a result of installing the high-efficiency motor instead of the standard motor. also, determine the simple payback period if the pu