Q:A truck engine transmits 25.5 kW (34.2 hp) to the driving wheels when the truc

Question

Q:A truck engine transmits 25.5 kW (34.2 hp) to the driving wheels when the truck is traveling at a constant velocity of magnitude 67.0 km/h (41.6 mi/h) on a level road.

(a) What is the resisting force acting on the truck?

answer = ________ N

(b) Assume that 62% 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 33.5 km/h? At 134.0 km/h? Give your answers in kilowatts and in horsepower.

can someone solve this question please fast.I need the answers

v = 33.5 km/h P = _______ kW P = _______ hp v = 134.0 km/h P = _______ kW P = _______ hp

Explanation / Answer

Power=force*velocity

Velocity=67 km/hr=18.6 m/s

So

Force=power/velocity=1370.15N

(b)

Friction force=0.62*1370.15=849.5 N

Air resistance=0.38*1370.15=k*v*v

At v=18.6

We got k=1.5

So at v=33.5 km/hr=9.3 m/s

Power=(1.5*9.3*9.3 + 849.5)*9.3=9.1 kW

For 134 km/hr=37.44 m/s

Power=((1.5*37.44*37.44)+849.5)*37.44=110.5 kW

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