Question

12) 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 3.3 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?

How much energy is lost to drag when the car travels 20 km at 29 m/s?

**Hint:** Figure out the power due to the drag. How
do you use this to figure out total work when velocity is constant?
Which kinematic model is most useful for relating time, velocity,
and displacement in this situation?

The car drives a distance 120 m up a section of road whose grade is 25% (the grade is the vertical rise of the road as a percent of the horizontal run of the road). The car's speed is 29 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?

**Hint:** Grade of the road is height divided by
horizontal distance. Model the road as a slanted slope and the rise
and run as the base and height of a right triangle whose hypotenuse
is the distance driven by the car. Why might the height the car
rises during this section of road be important from the perspective
of energy? What is the power associated with gravitational
work?

Answer #1

12) 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...

12) 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+Cv^2 For a Camry, these coefficients are
estimated to be A=117.130 N, B=1.800...

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do all five questions
Question 1
20 pts
Ignoring the effects of air resistance, if a ball falls freely
toward the ground, its total mechanical energy
Group of answer choices
increases
remains the same
not enough information
decreases
Flag this Question
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