A ship RADAR unit uses 315 watts and a radio uses 50 watts. If the equipment is connected to a 50 ampere-hour battery rated at 12.6 volts, how long will the battery last?
⢠Battery capacity in ampere-hours (Ah) and how to convert that into watt-hours (Wh) using voltage ⢠Power (watts) relationship with energy and time: ( P = \frac{E}{t} ) ⢠Adding the total power draw of multiple devices (RADAR + radio)
⢠First, figure out how much energy the battery can supply in watt-hours using its ampere-hour rating and voltage. What multiplication will give you that? ⢠Next, add the power used by the RADAR and the radio to find the total power draw. Once you know total watts and total watt-hours available, how do you solve for time? ⢠After you get time in hours from ( t = \frac{E}{P} ), how will you convert the decimal hours into hours and minutes to compare with the choices?
⢠Be sure you convert ampere-hours to watt-hours correctly using the battery voltage: ( \text{Wh} = \text{Ah} \times \text{V} ) ⢠Double-check you add both loads (315 W + 50 W) before calculating time; donāt treat them separately. ⢠After computing the time in hours, convert the fractional part of an hour to minutes by multiplying by 60, then compare carefully with the options.
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