A jetmotor is pushing the plane 50 000 Newton.How big of the work does motor do in 1 km?
work done W=F.s where F=force and s= the displacement due to force. Therefore W=50000*1000=5*10^7Nm or J
See if the answer here: http://web2.0calc.com/questions/piece-that-weighs-0-35-kg-is-falling-from-45-m-high gives you a clue.
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+33616 
