Two plane mirrors are placed 75 cm apart with their mirrored surfaces parallel and facing each other. If the mirrors are 10 cm wide, at what angle should a beam of light be incident at one end of one mirror so that it just strikes the far end of the other?

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