A disk is initially at motionless, then a motor is turned on and the disk begins to spin. If second the angular acceleration of the disk is a constant 3.5 r a d / s 2 , how many complete revolutions does the disk make in 9 seconds?

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