Final answer:
The rate of gasoline usage for a car that uses 3 gallons in 1 hour is 100 kW, which is calculated by converting the total energy in megajoules to joules and then dividing by the number of seconds in an hour.
Step-by-step explanation:
The question asks for the rate of gasoline usage in watts, given that 3 gallons of gasoline are used in 1 hour and knowing that 1 gallon contains approximately 120 megajoules (MJ) of energy. To find this, we can first calculate the total energy used, which is 3 gallons multiplied by 120 MJ, and then divide that by the time in seconds to find the rate.
Firstly, compute the total energy: 3 gallons * 120 MJ/gallon = 360 MJ. Since 1 watt is equal to 1 joule per second, we need to convert megajoules to joules (1 MJ = 1,000,000 J) and an hour to seconds (1 hour = 3600 seconds). Thus, we have:
360 MJ = 360 * 1,000,000 J = 360,000,000 J
360,000,000 J / 3600 seconds = 100,000 watts (or 100 kW)
Therefore, the rate of gasoline usage is 100,000 watts or 100 kW when driving for an hour using 3 gallons of gasoline.