Suppose the Energy Carried by an Electron in an Old-fashioned Tv Tube

Page 323 - College Physics For AP Courses

P. 323

          Chapter 7 | Work, Energy, and Energy Resources 311 25. (a) How loftier a hill can a auto coast up (engine disengaged) if work done by friction is negligible and its initial speed is 110 km/h? (b) If, in actuality, a 750-kg auto with an initial speed of 110 km/h is observed to coast upwards a hill to a top 22.0 m above its starting point, how much thermal energy was generated by friction? (c) What is the average force of friction if the hill has a slope  above the horizontal? 7.6 Conservation of Energy 26. Using values from Table seven.one, how many Deoxyribonucleic acid molecules could exist broken by the energy carried by a single electron in the beam of an old-fashioned TV tube? (These electrons were not dangerous in themselves, simply they did create dangerous 10 rays. Later on model tube TVs had shielding that absorbed x rays earlier they escaped and exposed viewers.) 27. Using energy considerations and bold negligible air resistance, show that a rock thrown from a span xx.0 m in a higher place h2o with an initial speed of 15.0 m/s strikes the h2o with a speed of 24.8 m/s independent of the management thrown. 28. If the free energy in fusion bombs were used to supply the free energy needs of the world, how many of the nine-megaton diverseness would exist needed for a twelvemonth'south supply of energy (using data from Tabular array seven.1)? This is not as far-fetched equally it may sound—there are thousands of nuclear bombs, and their free energy tin be trapped in hole-and-corner explosions and converted to electricity, as natural geothermal energy is. 29. (a) Employ of hydrogen fusion to supply energy is a dream that may be realized in the next century. Fusion would be a relatively clean and almost limitless supply of energy, every bit can exist seen from Tabular array vii.i. To illustrate this, calculate how many years the present energy needs of the globe could exist supplied past one millionth of the oceans' hydrogen fusion energy. (b) How does this time compare with historically pregnant events, such as the elapsing of stable economic systems? 7.7 Ability xxx. The Crab Nebula (run across Figure 7.41) pulsar is the remnant of a supernova that occurred in A.D. 1054. Using data from Table 7.3, calculate the gauge gene by which the power output of this astronomical object has declined since its explosion. Figure vii.41 Crab Nebula (credit: ESO, via Wikimedia Commons) 31. Suppose a star grand times brighter than our Sun (that is, emitting grand times the ability) of a sudden goes supernova. Using information from Tabular array vii.3: (a) By what factor does its power output increase? (b) How many times brighter than our unabridged Milky Way galaxy is the supernova? (c) Based on your answers, discuss whether information technology should be possible to observe supernovas in afar galaxies. Note that there are on the club of  appreciable galaxies, the average brightness of which is somewhat less than our own milky way. 32. A person in proficient physical condition can put out 100 W of useful power for several hours at a stretch, perhaps by pedaling a mechanism that drives an electrical generator. Neglecting any issues of generator efficiency and practical considerations such as resting fourth dimension: (a) How many people would it take to run a 4.00-kW electrical clothes dryer? (b) How many people would it take to supervene upon a large electrical power establish that generates 800 MW? 33. What is the cost of operating a three.00-Due west electric clock for a year if the price of electricity is $0.0900 per    ? 34. A large household air conditioner may consume 15.0 kW of power. What is the toll of operating this air conditioner 3.00 h per day for xxx.0 d if the cost of electricity is $0.110 per    ? 35. (a) What is the average ability consumption in watts of an apparatus that uses     of energy per twenty-four hour period? (b) How many joules of free energy does this appliance swallow in a year? 36. (a) What is the boilerplate useful power output of a person who does   of useful work in 8.00 h? (b) Working at this rate, how long volition it accept this person to lift 2000 kg of bricks one.fifty m to a platform? (Work done to elevator his body tin can be omitted because it is not considered useful output here.)                  

Share this post