Answer :
The specific energy consumption of the electric train is approximately X kWh/km.
To calculate the specific energy consumption, we need to consider the energy consumed during each phase of the train's motion and then calculate the total energy consumption. Let's go through each phase step by step:
(i) Uniform acceleration: The acceleration is given as 2-5 km/hr/sec for 60 seconds. We can calculate the average acceleration as (2 + 5) / 2 = 3.5 km/hr/sec. Converting this to m/s^2, we get 3.5 * (1000/3600) = 0.9722 m/s^2. The time duration is 60 seconds, so we can calculate the distance covered during acceleration using the equation s = (1/2) * a * t^2, where s is the distance, a is the acceleration, and t is the time. Plugging in the values, we get s = (1/2) * 0.9722 * (60^2) = 1741.56 meters. The work done during this phase can be calculated as W = m * g * s, where m is the mass of the train, g is the gravitational acceleration, and s is the distance. Converting the mass to kilograms (500 tonnes = 500,000 kg) and plugging in the values, we get W = 500,000 * 9.8 * 1741.56 = 8,554,082,400 Joules.
(ii) Constant speed: During this phase, there is no acceleration, so no additional work is done. We only need to consider the energy consumed due to resistance. The resistance force can be calculated as F_res = m * g * R, where R is the resistance in N/tonne. Converting the mass to tonnes, we have F_res = 500 * 9.8 * 25 = 122,500 N. The distance covered during this phase can be calculated using the formula s = v * t, where v is the constant speed in m/s and t is the time duration in seconds. Converting the speed to m/s (5 km/hr = 5 * 1000 / 3600 = 1.3889 m/s) and the time duration to seconds (5 minutes = 5 * 60 = 300 seconds), we get s = 1.3889 * 300 = 416.67 meters. The work done due to resistance during this phase is W = F_res * s = 122,500 * 416.67 = 51,041,750 Joules.
(iii) Coasting: During coasting, there is no acceleration or resistance force, so no additional work is done.
(iv) Dynamic braking: The train is brought to rest using dynamic braking, which converts the kinetic energy of the train into electrical energy. The braking force can be calculated as F_brake = m * a_brake, where a_brake is the deceleration in m/s^2. Converting the deceleration to m/s^2 (3 kmph = 3 * 1000 / 3600 = 0.8333 m/s^2), we have F_brake = 500 * 0.8333 = 416.67 N. The distance covered during braking can be calculated using the equation s = (v^2) / (2 * a_brake), where v is the initial velocity in m/s. The train comes to rest, so the initial velocity is the speed during the coasting phase, which is 0.
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