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According to the source, what is the approximate most fuel-efficient cruising speed range for a typical car?
A40 to 50 km/h
B10 to 20 km/h
C150 to 160 km/h
D70 to 80 km/h
Answer & Solution
Correct answer: D. 70 to 80 km/h
1. A specific range is given for the most fuel-efficient cruising speed of a car.
2. That range is about 70 to 80 km/h, or roughly 45 to 50 mi/h.
3. Speeds much lower waste efficiency at low engine load, and speeds much higher lose efficiency to the drag force growing with the square of speed.
4. The other ranges offered are either far too slow or far too fast to match that stated figure.
_Source: OpenStax College Physics (CC BY 4.0), Ch 5 "Further Applications of Newton's Laws: Friction, Drag, and Elasticity", section 5.2 Drag Forces_
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