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Automotive Power I. A truck engine transmits 28.0 kW (37.5
Chapter 3, Problem 100P(choose chapter or problem)
Automotive Power I. A truck engine transmits 28.0 kW (37.5 hp) to the driving wheels when the truck is traveling at a constant velocity of magnitude 60.0 km/h (37.3 mi/h) on a level road. (a) What is the resisting force acting on the truck? (b) Assume that 65% of the resisting force is due to rolling friction and the remainder is due to air resistance. If the force of rolling friction is independent of speed, and the force of air resistance is proportional to the square of the speed, what power will drive the truck at 30.0 km/h? At 120.0 km/h? Give your answers in kilo watts and in horsepower.
Questions & Answers
QUESTION:
Automotive Power I. A truck engine transmits 28.0 kW (37.5 hp) to the driving wheels when the truck is traveling at a constant velocity of magnitude 60.0 km/h (37.3 mi/h) on a level road. (a) What is the resisting force acting on the truck? (b) Assume that 65% of the resisting force is due to rolling friction and the remainder is due to air resistance. If the force of rolling friction is independent of speed, and the force of air resistance is proportional to the square of the speed, what power will drive the truck at 30.0 km/h? At 120.0 km/h? Give your answers in kilo watts and in horsepower.
ANSWER:Solution 100P Step 1: Data given Power 280 KW = 28000 W Velocity v = 60.0 km /hr = 16.67 m/s We need to find the resisting force acting on the truck We have relation P = F × v Using this we shall obtain the force acting on the truck F = P/v Substituting values we get F = 28000 W/16.67 m/s F = 1679.6 N This can be approximated to 1680 N Hence the total resistance force acting on the truck is 1680N