I have calculated a b and c but can\'t figure out d Answer in units of MJ. (a) A

Question

I have calculated a b and c but can't figure out d

Answer in units of MJ.

(a) A modern light bus of mass 6000 kg accelerates from rest to 16m/s (58 kph) and then slows to a stop in the traffic.

How much energy is transferred into kinetic energy going from restto 16 m/s?

(b) It experiences drag and rolling friction forces which average800 N in total. What is the energy dissipated dueto

these drag and friction forces in a 1.0 km trip?

(c) If the bus starts and stops on average 3 times in 1.0km, what total energy is required?

(d) The makes of this bus claim that on typical suburbantrips, such as described above, the bus uses 25 litre ofdiesel

per 100 km. Take the energy content of diesel as 36 MJ/litre.Compare the energy per km based on fuel

consumption with your answer in (c). Give the main reason for thedifference between these two figures.

Explanation / Answer

(a)   energy transfered into kinetic energy is(1/2)(6000kg)(16m/s)2 =768000J =  0.768MJ (b)   Energy dissipated in the drag and rollingis (800N)(1000m) = 800000J = 0.8MJ (c)   total energy required is 3(0.768MJ) =2.304MJ (d)   for travelling of 1km the energy requiredis 2.304MJ. for 100km energy required is 230.4MJ. but energy content of the diesel is 36MJ/litre therefore diesel required is (230.4MJ)/(36MJ/litre) =6.4L here we should also condsider the loss of energy due to dragforce . that is why we got the difference in teh two figures.

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