Power and energy are often used interchangeably, but they are quite different. Energy is measured in units of joules ( J ) or Calories (Cal), where \( 1 \mathrm{Cal}=4184 \mathrm{~J} \). On the other hand, power is the rate at which energy is used and is measured in watts (W; \( 1 \mathrm{~W}=1 \mathrm{~J} / \mathrm{s}) \). Other useful units of power are kilowatts ( kW ) and megawatts \( \left(1 \mathrm{MW}=10^{6} \mathrm{~W}\right) \). If energy is used at a rate of 1 kW for 1 hr , the total amount of energy used is 1 kilowatt-hour ( kWh\( ) \), which is \( 3.6 \times 10^{6} \mathrm{~J} \). Suppose the power function of a large city over a 24 -hr period is given by \( P(\mathrm{t})=\mathrm{E}^{\prime}(\mathrm{t})=345-230 \sin (\pi / / 12) \), where P is measured in MW and \( \mathrm{t}=0 \) corresponds to \( 6: 00 \) p.m. (see accompanying figure). Complete parts (a) through (d) below. Click the icon to view the graph of \( \mathrm{P}(\mathrm{t})=\mathrm{E}^{\prime}(\mathrm{t})=345-230 \sin (\pi \mathrm{t} / 12) \). (Simpiry your answer.) c. Fission of 1 gram of uranium- \( 235(\mathrm{U}-235) \) produces about \( 16,000 \mathrm{kWh} \) of energy. How many grams of uranium are needed to meet the energy needs of the city for 1 day? For 1 yr ? The amount of uranium needed in a day is 518 g . (Simplify your answer. Round to the nearest integer as needed.) The amount of uranium needed in a year is \( \square \mathrm{g} \). (Simplify your answer.)
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The Deep Dive
To find the amount of uranium needed to meet the city's energy needs for one year, first calculate the total energy required in a day. Since the city uses 518 grams of uranium in a day, multiply that by the number of days in a year: \( 518 \, \text{g/day} \times 365 \, \text{days} = 189070 \, \text{g} \). Rounding to the nearest integer, the total amount of uranium needed in a year is about 189,070 grams. Now, let's add a little context! Uranium-235 might seem like a superhero of energy production, but extracting it requires extensive processes, including mining and enrichment, which are vital to producing fuel for nuclear power reactors. One gram of uranium-235 is enough to produce an astonishing amount of energy, highlighting the power within even the smallest particles—impressive, huh?