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To maintain a constant speed, the force provided by a car’s engine must equal the drag force plus the force of friction of the road (the rolling resistance).

(a) What are the drag forces at 70 km/h and 100 km/h for a Toyota Camry? (Drag area is 0.70m2)
(b) What is the drag force at 70 km/h and 100 km/h for a Hummer H2? (Drag area is 2.44m2) Assume all values are accurate to three significant digits.

1 Answer

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Final answer:

The magnitudes of drag forces at different speeds for a Toyota Camry and a Hummer H2 depend on the vehicles' speed, frontal area, and the drag coefficient, but cannot be calculated precisely without the values for the drag coefficient.

Step-by-step explanation:

When considering the drag forces acting on vehicles at constant speeds, we typically use the drag equation, which states that the drag force on an object moving through air is proportional to the square of its speed, its frontal area, and the air density.

Additionally, it depends on a dimensionless quantity known as the drag coefficient. Given that we don’t have the drag coefficient values for the Toyota Camry and Hummer H2, we cannot calculate the exact magnitudes without additional information. Generally, at higher speeds, the drag force increases significantly.

For instance, doubling the speed can result in a fourfold increase in the drag force. This is important for fuel efficiency, as maintaining high speeds requires increasingly more engine power to overcome air drag.

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