PRIN.OF HIGHWAY ENGINEERING&TRAFFIC ANA.
7th Edition
ISBN: 9781119610526
Author: Mannering
Publisher: WILEY
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Chapter 2, Problem 19P
To determine
The unloaded braking efficiency.
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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?
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.
A level test track has a coefficient of road adhesion of 0.80, and a car being tested has a coefficient of rolling friction that is approximated as 0.018 for all speeds. The vehicle is tested unloaded and achieves the theoretical minimum stop in 180 ft (from brake application). The initial speed was 60 mi/h. Ignoring aerodynamic resistance, what is the unloaded braking efficiency?
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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- A 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_forwardA car is traveling at 70 mi/h on a level section of road with good, wet pavement. Its antilock braking system (ABS) only starts to work after the brakes have been locked for 100 ft. If the driver holds the brake pedal down completely, immediately locking the wheels, and keeps the pedal down during the entire process, how many feet will it take the car to stop from the point of initial brake application? (The braking efficiency is 80% with the ABS not working and 100 % with the ABS working. Use theoretical stopping distance and ignore air resistance. Let frl = 0.02 when the brakes are locked, but complete the frl once the ABS becomes active.)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 driver is traveling at 90 mi/h down a 3% grade on good, wet pavement. An accident investigation team noted that braking skid marks started 410 ft before a parked car was hit at an estimated 45 mi/h. Ignoring air resistance, and using theoretical stopping distance, what was the braking efficiency of the car? If the car’s antilock-braking system was effective (no sliding wheels on the pavement), what would the crash speed be?arrow_forwardQuestion-- 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 along the horizontal.arrow_forwardA 3500-lb vehicle (CD = 0.38, A_f= 26 ft^2, p =0.002378 slugs/ft^3) is driven on a surface with a coefficient of adhesion of 0.5, and the coefficient of rolling friction is approximated as 0.015 for all speeds. Assuming minimum theoretical stopping distances, if the vehicle comes to a stop 260 ft after brake application on a level surface and has a braking efficiency of 0.82, what was its initial speed (a) if aerodynamic resistance is considered and (b) if aerodynamic resistance is ignored?arrow_forward
- A 2400-lb vehicle (CD = 0.38, Af = 26 ft², and p 0.002378 slugs/ft³) is driven on a surface with coefficient of adhesion equal to 0.8 and a coefficient of rolling friction of 0.014 at all speeds. Assuming minimum theoretical stopping distances, if the vehicle comes to a stop 200 ft after brake application on a level surface and has a braking efficiency of 0.85, what was its initial speed (a) considering aerodynamic resistances, and (b) ignoring aerodynamic resistance?arrow_forwardA student trying to test the braking ability of his car, determined that he needed 32 ft. More to stop his car downhill on a particular road than uphill when driving at 55 mph. Assuming that the coefficient of friction between the tires and the pavement is 0.30. Determine the braking distance downhill and the percent grade of the highway at that section of the road.arrow_forwardA car is driving at 75 mph down a 4.0 % grade on poor, wet pavement. The car's braking efficiency is 90%. The driver saw an object which is 480 ft away and applied the brake, and his reaction time was 1.0 second. The car's antilock braking system (ABS) works. Just after seeing the object, which of the following is closest to the distance (in ft) traveled before applying the brake? (Assume theoretical stopping distance ignore air resistance and let yb= 1.04 and fr = 0.015). 153 ft B) 127 ft 135 ftarrow_forward
- A car is traveling at 60 mi/h on good, wet pavement. It has a wheelbase of 110 inches with the center of gravity 50 inches behind the front axle and at a height of 24 inches above the pavement surface. Determine the percentage of braking force that the braking system should allocate to the rear axle.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_forwardQ-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 along the horizontal.arrow_forward
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