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27 Nov 2019

the coefficient of static friction between steel train wheels and steel rails is .58. the engineer of a train moving at 140 km/h spots a stalled car on the tracks 150 meters ahead. if he applies the brakes so that the wheels don't slip, will the train stop in time?

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Keith Leannon
Keith LeannonLv2
13 Jun 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

In certain cities, parking spaces are at a premium and anyavailable surface will be used for parking, even highly slopedroofs. Consider the SUV parked in the picture above. If you are thedriver, how can you be sure that your car won’t flip overbackwards?
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1. First, let’s assume that the angle θ is 30 degrees (note thewheels are locked and don’t roll) and the car is not moving. Whatis the magnitude of the normal force from the road on the frontwheels (top of incline)? On the back wheels (bottom of incline)?These normal force are unequal- why?
2. Now let’s take the situation to the extreme: what is the maximumvalue of the angle θ which is possible, if the SUV is to remain instatic equilibrium? First, determine the maximum angle that the carwon’t slide, and then determine the maximum angle that the carwon’t rotate. What happens to the SUV first if the angle isexceeded? What is the normal force on the front (top of incline)wheels in this situation?
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A sports car claims that it can start from rest and reach 60 mph(26.8 m/s) in a distance of 33.5 meters. To reach its maximummspeed, it accelerates at this constant rate for 11.25seconds.

a) How many seconds does it take to reach 60 mph?
- I got 1.25 seconds
b) What is the maximum speed of this car?
- Using kinematics I got 120.6 m/s
c) If the mass is 1900 kg, what force must the car provide to keepit traveling at this maximum speed ( Hint: don't forgetfriction)

- I know that Fnet= mass x acceleration, and that gives me 1900 x10.72 = 20,368 N
but this is not taking into account friction. What role doesfriction play and how can I calculate it properly?

d) I was driving this car at a maximum speed on a test track when adeer ran out in front of me. My reaction time was 0.5 seconds,before I hit the brakes. Assuming that the engine is no longerapplying any forward force, and my wheels lock up, how far will Itravel before I come to a stop after seeing the deer (give answerin miles, using: 1 Km = 0.62 miles)?

e) How much time will elapse from the time that I see the deeruntil I stop?

A sports car claims that it can start from rest and reach 60mph (26.8 m/s) in a distance of 33.5 meters. To reach its maximummspeed, it accelerates at this constant rate for 11.25seconds.

a) How many seconds does it take to reach 60 mph?
- I got 1.25 seconds
b) What is the maximum speed of this car?
- Using kinematics I got 120.6 m/s
c) If the mass is 1900 kg, what force must the car provide tokeep it traveling at this maximum speed ( Hint: don't forgetfriction)
- I know that Fnet= mass x acceleration, and that gives me1900 x 10.72 = 20,368 N
but this is not taking into account friction. What role doesfriction play and how can I calculate it properly?
d) I was driving this car at a maximum speed on a test trackwhen a deer ran out in front of me. My reaction time was 0.5seconds, before I hit the brakes. Assuming that the engine is nolonger applying any forward force, and my wheels lock up, how farwill I travel before I come to a stop after seeing the deer (giveanswer in miles, using: 1 Km = 0.62 miles)?
e) How much time will elapse from the time that I see the deeruntil I stop?

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