7th Edition
ISBN: 9781119610526
Author: Mannering
Publisher: WILEY

Concept explainers

Book Icon
Chapter 2, Problem 1P
To determine

The power required to overcome the aerodynamics drag.

Expert Solution & Answer
Check Mark

Answer to Problem 1P

The power required to overcome the aerodynamics drag is 57.19hp

Explanation of Solution


Drag Coefficient of sports car, CD = 0.30

Front area of the car, A=21ft2

Speed of the car, V = 110mi/h

Density, ρ = 0.002378slugs/ft2

Formula Used:

The power required to overcome the aerodynamic drag is

  P = F × V


Force =

Velocity = V


The required power is calculated by power equation

  P = F × V ..................... (1)

We know that

Force applied on caris given by

  F = 12ρACDV2 ...................... (2)


Density = ρ

Front Area of the Car = A

Drag coefficient = CD

Rearranging the equation (1) as

  P = F × V

  P = (12 ρACD×V2) ×(V) 

  P = (12 ρACD)×V3   .................. (3)

To calculate power in (lb-ft/r), we have to convert the velocity from mi/h to ft / sec

  V = 110 mi/h = 110×52803600ft/s

As -

  1mi/h = 5280 ft3600 sec

Put the given values in equation (3)

  P = (12  ρACD)×V3P = (12×0.002378×21×0.3)×( 110×5280 3600)3

  P = 31455.364 lb-ft/s .......................... (4)

But we want the power in hp -

We know that - 1 lb-ft/s  = 1550hp 

So, the calculated power of equation (4) is converted into hp as

  P = 31455.364550hpP = 57.19 hp



Thus, the power required to overcome the aerodynamics drag is 57.19hp

Want to see more full solutions like this?

Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Students have asked these similar questions
The pilot of a jet transport brings the engines to full takeoff power before releasing the brakes as the aircraft is standing on the runway. The jet thrust remains constant, and the aircraft has a near-constant acceleration of 0.32g (where g is the gravitational acceleration). If the takeoff speed is 208 km/h, calculate the distance (m) required to takeoff.
5) A car is traveling along a straight road with an acceleration of a = 1/4 * s ^ (1/4) (m/s^ 2 ) Determine the velocity when the car travels 2 (m).
In traveling a distance of 3 km between points A and D, a car is driven at 100 km/hr from A to B for t seconds. If the brakes are applied for 4 sec between B and C to give a car uniform deceleration from 100 kmph to 60 kmph and it takes ' t ' seconds to move from C to D with a uniform speed of 60 kmph, determine the value of ' t '.
Knowledge Booster
Background pattern image
Civil Engineering
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, civil-engineering and related others by exploring similar questions and additional content below.
Similar questions
Recommended textbooks for you
Text book image
Traffic and Highway Engineering
Civil Engineering
Author:Garber, Nicholas J.
Publisher:Cengage Learning