Download the App!

Get 24/7 study help with the Numerade app for iOS and Android! Enter your email for an invite.

Get the answer to your homework problem.

Try Numerade free for 7 days

Like

Report

$\bullet$ $\bullet$ Automobile accident analysis. In an auto accident, a carhit a pedestrian and the driver then slammed on the brakes tostop the car. During the subsequent trial, the driver's lawyerclaimed that the driver was obeying the posted 35 mph speedlimit, but that the limit was too high to enable him to see andreact to the pedestrian in time. You have been called as thestate's expert witness. In your investigation of the accident site,you make the following measurements: The skid marks madewhile the brakes were applied were 280 ft long, and the tread onthe tires produced a coefficient of kinetic friction of 0.30 withthe road. (a) In your testimony in court, will you say that thedriver was obeying the posted speed limit? You must be able toback up your answer with clear numerical reasoning duringcross-examination. (b) If the driver's speeding ticket is $\$ 10$ foreach mile per hour he was driving above the posted speed limit,would he have to pay a ticket, and if so, how much would it be?

(a) $v_{1}=50 \mathrm{mi} / \mathrm{h}$(b) fine $=150 \mathrm{S}$

Physics 101 Mechanics

Chapter 7

Work and Energ

Physics Basics

Applying Newton's Laws

Kinetic Energy

Potential Energy

Energy Conservation

Rutgers, The State University of New Jersey

University of Washington

University of Winnipeg

Lectures

03:47

In physics, the kinetic en…

04:05

In physics, a conservative…

08:54

Legal Physics. In an auto …

02:35

04:36

$\bullet$$\bullet$ Acciden…

10:36

Automobile Accident Analys…

07:14

You have been hired as an …

07:07

17:33

You are called as an exper…

01:39

Traffic Court. You are cal…

10:24

You testify as an expert w…

04:40

05:12

You are driving your car o…

03:42

An accident reconstruction…

10:07

08:53

A police officer is invest…

04:44

You're in traffic cou…

01:37

In Exercises 38 and $39,$ …

02:22

Automotive Safety Traffic …

03:25

A car skids 18 m on a leve…

01:03

To estimate the speed at w…

07:30

Accident Analysis. Two car…

Okay, So in this problem, we need to use thie conservation off energy. Now we see that Ah, initially when the driver applied brake, then there was the nation form of kinetic energy, potential energy and this other form of energy, which is the non conservative force due to friction that should be equal to the final kind of the energy and the final potential eternity. Now we can see here few things like our final velocity, the F zero, so we can ignore the final potential energy part. On top of it, we can also ignored the difference between why, if minus why? Because is the car was slight going horizontally. That means there is no change in the white direction. So there's no changing gravitational potential energy. So m d Y zero for both of the cases. So this one is zero, and this one is here as well. So let's put them zero. It's all we have now is w other which is equal to negative one over two and the I squared Onda blue Other is thief friction thie worked on due to friction which is negative. Mu K Times md is equal to negative half off and the ice world. Now, muche is thie coefficient ofthe kind of friction and MDs in which is the normal force. And we have to multiply the displacement to wait to get the water. So what we did here is worked on his f k times s where f Kay's new okay, times and normal force And this Norman forces md. So that's how we got work done. And since the friction is working opposite to the direction of the displacement, So that's why there's a native China in front of it. And from here, if we solve for V I and see that the eye is square root off to nuke a time C times s we know values and we can plug them and calculate the velocity and figure out whether the driver speed driver was feeding or not. So for G, we have 32.18 foot per second squared as gravity and essays to 80 foot. From here we get the velocity as 70 3.5 foot per second from there. If we convert that miles first are we have 73.5 for for second times 16 mice for hours divided by 88. But per second, which gives us approximately 50 miles per hour, says we, you can clearly see that the driver was 15. My mind's for our over the posted limit because the posted limit wass 30 miles 35 miles per hour. So he was 15 mice per hour over the posted speed limit. So that means, if his 15 miles per hour over the speed limit, So he has to pay a ticket off $10 our minds for our And since he was 15 miles over, so he'll be paying and fine off 1 $50. Thank you.

View More Answers From This Book

Find Another Textbook

Numerade Educator

In physics, the kinetic energy of an object is the energy which it possesses…

In physics, a conservative force is a force that is path-independent, meanin…

Legal Physics. In an auto accident, a car hit a pedestrian and the driver th…

$\bullet$$\bullet$ Accident analysis. You have been called to testify as an<…

Automobile Accident Analysis. You are called as an expert witness to analyze…

You have been hired as an expert witness in a court case involving an automo…

You are called as an expert witness to analyze the following auto accident: …

Traffic Court. You are called as an expert withess in the trial of a traffic…

You testify as an expert witness in a case involving an accident in which ca…

You are called as an expert witness in a trial for a traffic violation. The …

You are driving your car on a straight road with a coefficient of friction b…

An accident reconstructionist is responsible for finding how fast cars were …

A police officer is investigating the scene of an accident where two cars co…

You're in traffic court, arguing against a speeding citation. You enter…

In Exercises 38 and $39,$ use the following information. When a car skids to…

Automotive Safety Traffic accident investigators can estimate the speed $S,$…

A car skids 18 m on a level road while trying to stop before hitting a stopp…

To estimate the speed at which a car was traveling at the time of an acciden…

Accident Analysis. Two cars collide at an intersection. Car $A,$ with a mass…

04:02

(1) Estimate the order of magnitude (power of ten) of: $(a) 2800$ , (b) $86.…

01:53

(III) The diameter of the Moon is 3480 $\mathrm{km}$ . (a) What is the surfa…

02:45

Singing in the shower! We all sound like great singers in the shower, due to…

00:49

What would be the radial (centripetal) acceleration of an astronaut standing…

04:09

(a) How many newtons does a 150 lb person weigh? (b) Should a veterinarian b…

06:11

$\bullet$ $\bullet$ A 350 kg roller coaster starts from rest at point $A$ an…

Loss of power! In December of $1989,$ a KLM Boeing 747 airplane carrying 231…

05:34

$\cdot$ The Eiffel Tower in Paris is 984 ft tall and is made mostly of steel…

02:41

(II) How much longer (percentage) is a one-mile race than a 1500 -m race (&q…

14:35

$\bullet$ A shell is launched at 150 $\mathrm{m} / \mathrm{s} 53^{\circ}$ ab…