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An electric train works at power 3000 kW and maintains a constant speed of 160 km h^-1...

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roshan-rox | (Level 1) Valedictorian

Posted October 2, 2013 at 5:18 AM via web

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An electric train works at power 3000 kW and maintains a constant speed of 160 km h^-1 , on a level track. Calculate the resistance to its motion.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted October 2, 2013 at 5:59 AM (Answer #1)

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The motor of the electric train needs to output power at 3000 kW to maintain a constant speed of 160 km/h.

Power is the rate at which work is done. Work is the product of force and distance. Power = `(F*d)/t` , but `d/t = v` . This gives `P = F*v` .

A power of 3000 kW is required to maintain a constant speed of 160 km/h. 160 km/h = `160*(1000/3600)` = `400/9` m/s

`3000*10^3 = (400/9)*F`

=> F = `(3000*10^3*9)/400`

=> F = `67.5*10^3` N

The resistance to the motion of the electric train is equal to `67.5*10^3` N

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