PRIN.OF HIGHWAY ENGINEERING&TRAFFIC ANA.
7th Edition
ISBN: 9781119610526
Author: Mannering
Publisher: WILEY
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Chapter 2, Problem 37P
To determine
The percentage braking force that the braking system should allocate to the rear axle.
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A car traveling at 45 mph on a poor, wet pavement has a braking efficiency of 87%. The
brakes were applied 100 feet before hitting an obstacle in the road. The road is uphill for 40
feet and then is level for the remainder of the way. The car had a maximum coefficient of
road adhesion in the sloped portion of the poor, wet roadway and but as soon as it started
going on the level portion its coefficient of road adhesion reduced to 0.3. Assuming that the
car struck the obstacle at 30 mph, what was the grade of the hill? Assume practical stopping
distance equation applies.
8 ft wheelbase
Rear-wheel drive
Center of gravity 17 inches above the road 4.1 ft behind the front axle.
The car weighs 2500 lb
Mechanical efficiency of the drivetrain is 93%
Wheel radius is 14 inches.
If the engine develops 190 ft-lb of torque and the overall gear reduction ratio is 7
to 1, what is the maximum acceleration from rest for the car? Assume good, dry,
and level pavement conditions.
6 A car is traveling at 20 mi/h on good, dry pavement at 5000 ft elevation. The front-wheel-drive car has a drag coefficient of 0.30, a frontal area of 20 ft2 and a weight of 2500 lb. The wheelbase is 110 inches and the center of gravity is 20 inches from the ground, 50 inches behind the front axle. The engine is producing 95 ft-lb of torque and is in a gear that gives an overall gear reduction ratio of 4.5. The radius of the drive wheels is 14 inches and the mechanical efficiency of the drivetrain is 90%. What would the acceleration of the car be if the driver was accelerating quickly to avoid a collision?
Chapter 2 Solutions
PRIN.OF HIGHWAY ENGINEERING&TRAFFIC ANA.
Ch. 2 - Prob. 1PCh. 2 - Prob. 2PCh. 2 - Prob. 3PCh. 2 - Prob. 4PCh. 2 - Prob. 5PCh. 2 - Prob. 6PCh. 2 - Prob. 7PCh. 2 - Prob. 8PCh. 2 - Prob. 9PCh. 2 - Prob. 10P
Ch. 2 - Prob. 11PCh. 2 - Prob. 12PCh. 2 - Prob. 13PCh. 2 - Prob. 14PCh. 2 - Prob. 15PCh. 2 - Prob. 16PCh. 2 - Prob. 17PCh. 2 - Prob. 18PCh. 2 - Prob. 19PCh. 2 - Prob. 20PCh. 2 - Prob. 21PCh. 2 - Prob. 22PCh. 2 - Prob. 23PCh. 2 - Prob. 24PCh. 2 - Prob. 25PCh. 2 - Prob. 26PCh. 2 - Prob. 27PCh. 2 - Prob. 28PCh. 2 - Prob. 29PCh. 2 - Prob. 30PCh. 2 - Prob. 31PCh. 2 - Prob. 32PCh. 2 - Prob. 33PCh. 2 - Prob. 34PCh. 2 - Prob. 35PCh. 2 - Prob. 36PCh. 2 - Prob. 37PCh. 2 - Prob. 38PCh. 2 - Prob. 39PCh. 2 - Prob. 40P
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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
- 1. The driver of a vehicle traveling at 80 kph up a grade requires 9 m less to stop after he applies the brakes than the driver travelling at the same initial speed down the same grade. If the coefficient of friction between the tires and pavement is 0.50, what is the percent grade and what is the braking distance down the grade. V,=80 kph V2=0 brakes are applied S-9 V,=80 kph V2=0 brakes are applied -S-arrow_forwardIn a certain situation it was estimated that 25% of the braking force was applied to the rear brakes in order for the car to develop the maximum forces required stop the car. If the total braking force developed was 5565 N and the road is wet (u = 0.6), wheelbase of 295 cm and a center of gravity 75 cm above the pavement and 120 cm behind the front axle. Determine the weight of the vehicle (N)arrow_forwardIn a certain situation it was estimated that 25% of the braking force was applied to the rear brakes in order for the car to develop the maximum forces required stop the car. If the total braking force developed was 5000 N and the road is wet (u = 0.52), wheel base of 290 cm and a center of gravity 64 cm above the pavement and 120 cm behind the front axle. Determine the weight of the vehicle (N).arrow_forward
- A 11120 N car is designed with a 310 cm wheelbase. The center of gravity is located 60 cm above the pavement and 105 cm behind the front axle. If the coefficient of road adhesion is 0.6, what is the maximum tractive effort that can be developed if the car is (a) front-wheel drive and (b) rear-wheel drive? From the previous question, how far back from the front axle would the center of gravity have to be to ensure that the maximum tractive effort developed for front- and rear-wheel drive options is equal?arrow_forwardA car is traveling at 76 mi/hr down a 3% grade on poor, wet pavement. The car's braking efficiency is 90%. The brakes were applied 320 ft before impacting an object. The car had an antilock braking system, but the system failed 200ft after the brakes had been applied (wheels locked). What speed was the car traveling at just before it impacted the object? (Assume theoretical stopping distance, ignore air resistance, and let Frl=0.015)arrow_forwardThe radius of a horizontal circular curve on a highway is 120 m. The design speed is 60 km/hour, and the design coefficient of lateral friction between the tyre and the road surface is 0.15. The estimated value of superelevation required (if full lateral friction is assumed to develop), and the value of coefficient of friction needed (if no superelevation is provided) will, respectively, be A B C 1 11.6 1 10.5 1 11.6 and 0.10 and 0.37 and 0.24arrow_forward
- Determine the horsepower developed by a passenger car traveling at a speed of 50-mi/h on an upgrade of 5% with a smooth pavement. The weight of the car is 4,500-lb and the cross-sectional area of the vehicle is 50 square-feet. Repeat this for a 24,000-lb truck with cross-sectional area of 100 square-feet and coefficient of drag of 0.5 traveling at 55-mi/h.arrow_forwardA rear-wheel-drive 2800-lb drag race car has a 170-inch wheelbase and a center of gravity 20 inches above the pavement and 140 inches behind the front axle. The owners wish to achieve an initial acceleration from rest of 22 ft/s 2 on a level paved surface. What is the minimum coefficient of road adhesion (in %) needed to achieve this acceleration? (Assume y m = 1.00.)arrow_forwardA 11120 N car is designed with a 310 cm wheelbase. The center of gravity is located 60 cm above the pavement and 105 cm behind the front axle. If the coefficient of road adhesion is 0.6, what is the maximum tractive effort that can be developed if the car is (a) front-wheel drive and (b) rear-wheel drive?arrow_forward
- a 2500-lb car designed with a 120-inch wheelbase. the center of gravity is located 22 inches above the pavement and 40 inches the front axle. if the coefficient of road adhesion is 0.6, how far back from the front axle would the center of gravity have to be to ensure that the maximum tractive effort developed for front- and rear- wheel-drive option is equal?arrow_forwardO-A vehicle is moving on a road of grade +4% at a speed of 20 m/s. Consider the coefficient of rolling friction as 0.46 and acceleration due to gravity as 10 m/s2. On applying brakes to reach a speed of 10 m/s, Find the required braking distance (in m, round off to nearest integer) along the horizontal.arrow_forwardCompute the braking distance for a car moving at an initial velocity of 60kph and a final velocity of 40 kph. slope of roadway is +5% Coefficient of friction between the pavement and tires = 0.15 perception-reaction time = 3/4 secarrow_forward
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