A 1000kg car accelerates from rest to 60mph (134m/s) in 10s. During this time, i
ID: 1307720 • Letter: A
Question
A 1000kg car accelerates from rest to 60mph (134m/s) in 10s. During this time, its engine was operating at 3600rpm. (a) Use the work-energy theorem to find the net work done by the car (Hint: there is no change in potential energy).
(b) Determine the number of cycles the engine goes through in 10s.
(c) How much work is done per cycle?
(d) Efficiency of an engine is given by ? =Wnet/QH. Now assuming that this engine has an efficiency of ?=20%, find the average heat flow into the engine in each cycle.
Explanation / Answer
a)
work done = change in K.E. = 1000 x 134^2 /2 -0 = 8978000 J
b) in 60 sec -> 3600 round
in 10 sec -> 3600/6 = 600 round
c) per cycle = 8978000 / 600 = 14963.33 J
d) 0.20 = 14963.33 / Qh
Qh = 74816.67 J
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