* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cochise College
Document related concepts
COCHISE COLLEGE PHYSICS HOMEWORK ASSIGNMENT A-13 POWER AND ENERGY VALUE: 60 Points Due Date: 1. If 270.0 m3 of water goes over a waterfall 53.0 m high every minute. (a) Calculate the power released in watts. (b) Convert this power to kilowatts. (c) Calculate how many kilowatthours of energy are released in one year. (d) If 50% of the power is extracted by turbine engines and converted to electrical energy, calculate the value of the energy generated in one year (in dollars) if one kilowatt.hour is worth 9 cents. 2. A 4.60 kg bowling ball is suspended from the ceiling as a simple pendulum by a cable. If the pendulum is 6.00 m long and is pulled back until the cable makes an angle of 42 with the vertical, calculate: (a) the potential energy of the bowling ball (b) the maximum kinetic energy that it will develop (c) the velocity of the bowling ball at the bottom of its swing. 3. An elevator and cable of mass 2600 kg contains a group of people of mass 500kg. An electric motor of 30% efficiency operates the elevator. (70% of the incoming electrical energy is lost in friction and heat.) If electrical energy costs the hotel 11 cents per kilowatthour, how much electrical energy in dollars does it take to move the elevator and its load up 32 floors? Assume that one floor equals 3.50 meters. (Calculate the work done in joules and then convert to kilowatthrs.) 4. An electric motor draws ½ horsepower while it is operating. The motor is used continuously for 12 hours a day to run an evaporative cooler. Assume that electrical energy costs 11 cents per kilowatthour. (a) What is the electrical cost for a 12 hour period? (b)If 12 hours per day is the normal average for summer use, then how much does running the evaporative cooler add to a typical electric bill for a month (30 days)? 5. Using the concept of conversion of potential energy to kinetic energy, calculate the speed of a pendulum bob hanging from a 70.0 m rope that has been deflected 14 from a vertical position and then released.. Calculate the speed (a) in m/s and (b) mi/hr. 6. If a football player of weight 220 lbs can carry a sack of concrete of weight 90 lbs up 3 flights of stair (30 ft total) in 18.0 sec, how much power in horsepower is he putting out?