Question

1. 13) There are several types of drag on a car other than air resistance. Effects having to do with the squeezing of the tires (rolling resistance) and frictional forces in the drivetrain (the system that transfers energy from the engine to the rotation of the wheels) also must be taken into account. Engineers use the following equation to model the total force due to these different effects
   
   Fdrag=A+Bv+Cv2Fdrag=A+Bv+Cv2
   
   For a Camry, these coefficients are estimated to be A=117.130A=117.130 N, B=1.800 N s/mB=1.800 N s/m, and C=0.368 N s2/m2C=0.368 N s2/m2.
   
   Suppose that the driver steadily accelerates the car from 0 km/hr to 100 km/hr over a 3.4 s. What is the magnitude of the work done by the drag forces?
   
   

   Hint: What is the instantaneous power of the drag? What is the relationship between that and the total work done by drag forces? Which kinematic model can you use to relate velocity, time, and acceleration?
   
   14) How much energy is lost to drag when the car travels 35 km at 31 m/s?

   Answer:  
   
   15) The car drives a distance 110 m up a section of road whose grade is 20% (the grade is the vertical rise of the road as a percent of the horizontal run of the road). The car's speed is 31 m/s. The car has a mass of 1543.60 kg. What is the minimum amount of power needed for the car to drive up this section of road, assuming perfect efficiency?

Answer 1