What is Stopping distance: Definition and 98 Discussions
Stopping sight distance is one of several types of sight distance used in road design. It is a near worst-case distance a vehicle driver needs to be able to see in order to have room to stop before colliding with something in the roadway, such as a pedestrian in a crosswalk, a stopped vehicle, or road debris. Insufficient sight distance can adversely affect the safety or operations of a roadway or intersection.
Stopping sight distance is the distance traveled during the two phases of stopping a vehicle: perception-reaction time (PRT), and maneuver time (MT). Perception-reaction time is the time it takes for a road user to realize that a reaction is needed due to a road condition, decide what maneuver is appropriate (in this case, stopping the vehicle), and start the maneuver (taking the foot off the accelerator and depressing the brake pedal). Maneuver time is the time it takes to complete the maneuver (decelerating and coming to a stop). The distance driven during perception-reaction time and maneuver time is the sight distance needed.
The design standards of the American Association of State Highway and Transportation Officials (AASHTO) allow 1.5 seconds for perception time and 1.0 second for reaction time.The values of stopping sight distance used in design represent a near worst-case situation. For design, a conservative distance is needed to allow a vehicle traveling at design speed to stop before reaching a stationary object in its path. A generous amount of time is given for the perception-reaction process, and a fairly low rate of deceleration is used. The design sight distance allows a below-average driver to stop in time to avoid a collision in most cases.
Driver perception/reaction distance is calculated by:
dPRT = driver perception-reaction distance, m (ft)
V = design speed, km/h (mph)
t = brake reaction time, in secondsBased on the results of many studies, 2.5 seconds has been chosen for a perception-reaction time. This time will accommodate approximately 90 percent of all drivers when confronted with simple to moderately complex highway situations. Greater reaction time should be allowed in situations that are more complex.
Braking distance is calculated by:
dMT = braking distance, m (ft)
V = design speed, km/h (mph)
a = deceleration rate, m/s2 (ft/s2)Actual braking distances are affected by the vehicle type and condition, the incline of the road, the available traction, and numerous other factors.
A deceleration rate of 3.4 m/s2 (11.2 ft/s2) is used to determine stopping sight distance. Approximately 90 percent of all drivers decelerate at rates greater than that. These values are within most drivers' ability to stay within his or her lane and maintain steering control. Also, most wet pavement surfaces and most vehicle braking systems are capable of providing enough braking force to exceed this deceleration rate.
Stopping sight distance (SSD) is the sum of reaction distance and braking distance
Homework Statement
A large box of mass M is moving on a horizontal surface at speed v_0. A small box of mass m sits on top of the large box. The coefficients of static and kinetic friction between the two boxes are μs and μk, respectively.
Find an expression for the shortest distance dmin in...
Hello,
This is an investigation I have been studying recently, can someone help with the following...
1. Homework Statement
Method:
1. Place a toy car at the top of a ramp.
2. Let it go.
3. Measure the distance it travels from the bottom of the ramp.
4. Add a 100 g mass to the car and...
Homework Statement
A crate is being transported on a flatbed truck. The coefficient of static friction between the crate and the bed is 0.470. What is the minimum stopping distance if the truck, traveling at 70 km/h, is to decelerate uniformly and the crate is not to slide forward on the bed...
Homework Statement
Calculate the braking distance for a car traveling at a speed of 35.0m/s down a hill at an angle of 10.0 degrees relative to the horizontal.
Homework Equations
F=ma
v=u + 2as[/B]
The Attempt at a Solution
The teacher briefly explained this in class saying that the total...
Forgive me if I have not posted this in the right place but I have a quick question. Say if you have a trailer on a truck, let's say a semi trailer, that has 2 axles on it. You measure the stopping distance from a certain speed. You then add another axle to the trailer that has brakes on it with...
Homework Statement
12.81[/B] A train traveling at 20m/s is brought to an emergency stop. During braking,
the acceleration is a=-(7/4)+(t/16) m/s^2, where t is the time in seconds measured
from when the brakes were applied. (a) Integrate the acceleration from t=0 to
t=16s using Euler's method...
This is problem 12.81 from Pytels Dynamics 2nd edition
1. Homework Statement
A train traveling at 20m/s is brought to an emergency stop. During braking,
the acceleration is a=-(7/4)+(t/16) m/s^2, where t is the time in seconds measured
from when the brakes were applied. (a) Integrate the...
I have been reading quite a lot about the Physics behind car dynamics and I have gotten to a point which keeps confusing me, namely - brake locking.
I understand brake locking as the situation when the wheels of the car do not rotate anymore but the car is still moving - this causes the tires...
As I have heard, for a moving object, stopping distance is proportional to the square of the speed. Is this true, and does this apply to angular movements such as body part movements?
No Template because thread was posted in non-homework forum
A car traveling at speed v takes distance d to stop after breaks are applied. What is the stopping distance if the car is initially traveling at speed 3.0v? Assume that the acceleration due to the braking is the same in both cases.
I...
Homework Statement
A car is stopped in a distance D by a constant friction force that is independent of the car's speed. What is the stopping distance (in terms of D) if
(a) The car's initial speed is tripled, and
(b) The speed is the same as it originally was but the friction force is tripled...
Homework Statement
an accident occurs up ahead on the highway. a driver traveling at 120km/h [e] reacts in 0.20s and applies the brakes causing an acceleration of 8.0m/s2 [w]. show that the stopping distance is 76 m.
what am i doing wrong? i changed the acceleration to match the directions, so...
Homework Statement
reaction time of a driver to brake is 0,5s in that time the speed is constant
the speed of a car is constant when he decides to slow down and to stop with -6,0 m/s2, the initial speed is 50 km/h
Calculate the total stopping distance of the car
Homework Equations
Ve= -6,0*t...
Homework Statement
Having trouble with the concept here and have gotten stuck!
A man is pushing a mobile machine down a corridor at a steady speed of 1.2 m/s. The machine’s mass is 55 kg. Another person who has been walking in front of the machine has suddenly stopped. If the man is able to...
Homework Statement
I am doing my IB Physics Individual Investigation on how mass affects the stopping distance of a small cart when colliding with an open box at the bottom of an inclined plane.
I wanted to know the relationship mass has with the stopping distance, similar to how a train...
< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >
A 50,000kg locomotive is traveling at 10m/s on a level track when the engines and brakes both fail. If there is a frictional force of 142N acting to slow it down, how far will it roll before it...
Homework Statement
A car of mass 1000 kg is cruising at 120 km/hr. At this velocity the drag and friction forces that the engine needs to work against is equivalent to 450 N.
(i) What is the propulsive power being delivered by the engine when cruising? (4 marks)
(ii) From a velocity of 100...
Homework Statement
Tests reveal that a normal driver takes about 0.75 s before he or she can react to a situation to avoid a collision. It takes about 3 s for a driver having 0.1% alcohol in his system to do the same. If such drivers are traveling on a straight road at 30 mph (44 ft/s) and...
Homework Statement
While traveling on the highway with your 1000kg car, at 115.2 km/h, where you’re ABS (automatic
braking system) is disabled. This means braking is relying solely on the friction of your tires with the road when they stop spinning. A dear jumps into the road 50 meters in...
Homework Statement
While traveling on the highway with your 1000kg car, at 115.2 km/h, where you’re ABS (automatic
braking system) is disabled. This means braking is relying solely on the friction of your tires with the road when they stop spinning. A dear jumps into the road 50 meters in...
Homework Statement
Homework Equations
## F = \frac{m(v-u)}{t}##
The Attempt at a Solution
The mass of cricket ball is greater than mass of plastic ball.
Change of velocity is same for both. Now since the rate of change of momentum of cricket ball is greater the force needed to bring it to...
Homework Statement
A tree is being transported on a flatbed trailer by a landscaper. If the base of the tree slides on the trailer, the tree will fall over and be damaged. If the coefficient of static friction between the trailer and the tree is 0.5, what is the minimum stopping distance of the...
Homework Statement
In order to stop a car in shortest distance on a horizontal road, one should,
(a) Apply brakes very hard so that the wheels stop rotating
(b) Apply the brakes hard enough to just prevent slipping
(c) Pump the brakes (press and release)
(d) Shut the engine off and not apply...
Homework Statement
Hi everyone, this is the attempted problem.
A car starts from rest and accelerates at 5m/s^2 for 15 seconds. It than decelerates at -2m/s^2 for an unknown time (say t').
Calculate how long it takes for the car to stop
Homework Equations
I know I should be used...
Ep = Ek
mgh = Ek
mgh = ½mv²
v = √2gh
As the collision is elastic, m1u1 + m2u2 = m1v1 + m2v2. It is known that m2 = 2m1.
m√2gh = 2m1v2
v2 = (m√2gh)/2m
v2 = (√2gh)/2
Force body diagram of m2:
̂̂̂̂̂̂Fnet = ma
Fnet = Fn + Fg + Ff
Fnet = Ff
m2a = Ff
a = Ff/m2
a = Ff/2m1
a =...
Hello have a question and am interested to find a simple equation to include mass as a variable regarding stopping distances of a car
In the UK highway code... a braking distance = 14m for a car at 30 mph (48 kph)
my questions are... if you load the car up fully (increase mass)... then...
According to test performed by the manufactures, an automobile with an initial speed of 75 km/h has a stopping distance of 25 m on a level road. assuming that no skidding occurs during breaking, what is the value of μ , between the wheels and the road required to achieve the stopping distance...
Homework Statement
A car is moving along a flat road at a constant 18ms^-1 it then applies the breaks with a force of 3600N
If this car is then moving down a hill at 18ms^-1 the same breaking force is applied is the cars stopping distance larger or smaller or the same?
Homework...
I just want to confirm if what I am doing is right, please correct me because my textbook gives me a different answer.
Homework Statement
The mass of a minibus with the driver is 1.5*10^3 kg. The driver is moving at a speed of 30m.s when he notices that the traffic lights ahead have turned...
Homework Statement
A skier skiing downhill reaches the bottom of a hollow with a velocity of 20m/s, and then coasts up a hill with a 10° slope. If the coefficient of kinetic friction is 0.10, how far up the slope will she travel before she stops?
Homework Equations
aΔt=v2-v1
d= 1/2(v1 +...
Homework Statement
When a car is traveling at 22 m/s on level ground, the stopping distance is found to be 22 m. This distance is measured by pushing hard on the brakes so that the wheels skid on the pavement. The same car is driving at the same speed down an incline that makes an angle of...
Homework Statement
The coefficient of friction is .48. The brakes are applied to a 1.05 x10^3 car traveling at 95km/hr. How far does the car move before it stops ? How long does it take for the car to stop?
Homework Equations
Fg = Fn, Fa= u x Fn, a=Fa/m, d=Vf^2-Vi^2/2a, t=d/v
The...
Homework Statement
A 290-N crate rides without constraints on the horizontal floor of a truck. The coefficient of static friction and the coefficient of kinetic friction between the crate and the truck are 0.32 and 0.16, respectively. If the truck is initially traveling at 18 m/s, what minimal...
In my physics textbook, it states that the stopping distance increases with the square of the intial speed. Could someone provide me with an example of why this is true?
Thank you
Homework Statement
A driver carelessly ignores the reduced speed limit of 40.0 km/h in a school zone and continues at 65 km/h. Assuming a good reaction time of 0.80 s, how many more metres will it take him to stop than if he had reduced his speed? Assume 2000kg car has a constant braking...
1. What is the meaning, when a graph of Stopping Distance vs. Kinetic Energy is made, of the slope of the line? Justify this answer by showing how y=mx+b corresponds to the quantities you actually plotted.D is given in CM, and KE given in \frac{g\times cm^{2}}{s^{2}}
Three points (From lab...
Hi All,
It's been a looong time since I've had to use/apply basic physics but I'm hoping I've come to the right place for help.
I am trying to help my brother-in-law with a speeding charge.
First question
The police allege he reached 100km/h within 38m of a corner.
The first...
Ok, this isn't a homework question, I've been out of school for quite some time but I'm having an argument with a buddy how to solve this - I know it's straight out of high school physics but it's been a loooooong time since high school physics... :)
You have a car going 44 ft/s - now you...
Homework Statement
A vehicle weighs 3000 lbf and has an initial velocity of 68 mph. If the braking system is designed to stop the vehicle at constant power, calculate the stopping distance in feet, if the stopping power is 100 hp.
m = 3000 lbf / 32.2 ft/s2 = 93.17 (lbf-s2)/ft
v = 68 mph...
Homework Statement
Human reaction times is sometimes worsened by alcohol. How much farther would a drunk driver's car travel before he hits the breaks than a sober drivers car? assume both cars are initially traveling 49 mi/h the sober driver takes .33s to hit the brakes and the drunk driver...
Homework Statement
I am given 3 variables, Vxi (initial velocity), Tr (reaction time), Ax (acceleration.
Now, I must make a formula for the braking distance.
Here are the variables: Vxi = 20 m/s, Tr = 0.60 s, Ax = -4 m/s^2
How would I construct there in a formula to get the total...
I was hoping you could help me with a stopping distance problem?
Reaction Time=1.5 seconds
Coefficient of Friction= .7
Distance=506 Feet
Ending Speed= 30mph
Starting Speed?
I was wondering you could help me figure out the original speed the car was traveling if after 506 feet braking...
A truck with a mass of 4500kg and a car with a mass 1500kg both apply the brakes at the same time, if the coefficient of friction is 0.15, and both vehicles are traveling at 20m/s, how far will it take each vehicle to stop?
Ff=0.15Fn
W=FappD
Ek2-Ek1=W
Fn=mg
Ek=1/2mv^2
for the truck...
Homework Statement
To avoid an accident, the driver of a 1000kg car moving 90km/h on a straight horizontal road steps o the brakes with maximum force. The car skids to a stop. The coefficient of kinetic friction between tires and road is 0.80. How far does the car travel during the skid...
Homework Statement
in an emergency stop on a level dry concrete road the magnitude of the friction force when sliding is approx 80% of the weight of the vehicle. What stopping distance is required for a vehicle traveling at 88km/h (24.444 m.s)?
Assume that all the wheels lock when the...
I don't understand these words: stopping distance and reaction time! Can anyone show me how to solve or the formula of stopping distance and reaction time!
What are the factors affect the stopping distance?
Like, there is a car is traveling at 70 m/hr, and its reaction time is 2 seconds...
Homework Statement
A car is traveling at 66.9 mi/h on a horizontal highway.
The acceleration of gravity is 9.8 m/s2 .
If the coefficient of friction between road and tires on a rainy day is 0.13, what is the minimum distance in which the car will stop? (1 mi = 1.609)
Answer in units of m...
Homework Statement
In an emergency stop on a level, dry concrete road, the magnitude of the friction force when sliding is approx 80% of the weight of the vehicle what is the stopping distance required for a vehicle traveling at 88km/h (24.444m/s). assume that all the wheels lock when the...
Homework Statement
determine the stopping distance for a car with an intitial speed of 26.9 m/s and a human reaction time of 0.9s for an acceleration of -4m/s^2
Homework Equations
x=vt t=v/a x=x+vt+.5at^2
The Attempt at a Solution
I used the second equation to find total...