Concept explainers
(a)
Estimate the force on sign board both orientations?
Answer to Problem 7.3CP
For position (A)
For position (B)
Explanation of Solution
Given information:
The sign board is
Velocity is equal to
The Reynolds’s number based on length
In above equation,
The drag co-efficient is defined as,
The drag force is defined as,
Assume, the air at
Calculation:
For position (A),
According to the definitions, the drag co-efficient is equal to,
Convert,
Calculate the drag force,
For position (B),
Calculate the Reynolds’s number,
Calculate the drag co-efficient,
Calculate the drag force,
Therefore, both sides
Conclusion:
For position (A)
For position (B)
(b)
Calculate the total drag for car-sign combination for both orientations?
Answer to Problem 7.3CP
For position (A)
For position (B)
Explanation of Solution
Given information:
The sign board is
Velocity is equal to
Drag co-efficient
Frontal area is equal to
The drag force is defined as,
Where,
Assume, the air at
Calculation:
Calculate the drag force for car,
Therefore,
The total drag for position (A),
The total drag for position (B),
Conclusion:
For position (A)
For position (B)
(c)
Calculate the horse power required for both orientations?
Answer to Problem 7.3CP
For position (A)
For position (B)
Explanation of Solution
Given information:
Velocity is equal to
The rolling resistance is equal to
The power required
In above equation,
Calculation:
Convert,
For position (A)
Calculate the power required,
Substitute,
Convert to horse power,
For position (B)
Calculate the power required,
Substitute,
Convert to horse power,
Conclusion:
For position (A)
For position (B)
(d)
Calculate the fuel efficiency for both orientations in
Answer to Problem 7.3CP
For position (A)
For position (B)
Explanation of Solution
Given information:
Velocity is equal to
Power delivered by engine per gallon of gasoline is equal to
The fuel efficiency is defined as,
Calculation:
Calculate the fuel efficiency,
For position (A),
For position (B),
Conclusion:
For position (A)
For position (B)
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Chapter 7 Solutions
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