Obviously, from the point view of efficiency, the higher the EER the better, but a higher EER is typically accom higher price. Consider two 12,000-Btu air conditioners, one with an EER of 7.8 and the other with a EER of 10. The difference in price is about 70 dollars. Assuming that the air conditioner will be operated for 6 hours daily during a period of 4 months every year, how long will it take to break even financially if you purchase the more expensive unit? Take the electricity to be 0.10dollar/(kilowatt. Hour). a) Less than a year b) about two year c) about three year d) about four year e) more than five years

1-10. need . physics. circular motion. 35 points

For problems 1-3, consider a simple dc brush motor with a permanent magnet stator. with an an consider a simple dc brush motor with a permanent magnet ae supply voltage of 100 v, the no-load speed of the motor is 1000 rpm. this motor can provide a torque of 1.9 n-m at 800 rpm drawing a current of 2 a current are both zero at no load.) 1. with an armature supply voltage of 100 v, the motor is operated at 900 rpm. what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input? what is the energy efficiency of the motor? with an armature supply voltage of 100 v, the motor is operated at 1100 rpm (where it acts as a generator). what torque input is required? what mechanical power is required what current is generated? what is the electrical power generated? what is the energy efficiency of the motor acting as a generator? 2. with an armature supply voltage raised to 120 v, the motor is operated at 1000 rpm. what is the no-load speed? what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input what is the energy efficiency of the motor? 3.

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.