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Car B is traveling a distance d ahead of car A. Both cars are traveling at 60 ft/s when the driver of B suddenly applies the brakes, causing his car to decelerate at 12 ft/s^2. It takes the driver of car A 0.75 s to react (this is the normal reaction time for drivers). When he applies his brakes, he decelerates at 15 ft/s^2. Determine the minimum distance d between the cars so as to avoid a collision.

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29 Mar 2021
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Related textbook solutions

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

Related questions

a)Car B is travelling a distanced, ahead of carA. Both cars are travelling at the same speed of 20km/s, when thedriver of B suddenly applies the brakes, causing hiscar todecelerate at 4 km /s2.It takes the driver of car A 0.8 s toreact(this is a normal reaction time for drivers). When he applieshisbrakes, he decelerates at 5 km /s2. We want to determine theminimum distance d between thetwo cars so as to avoid a collision.

Seat belts and airbags save lives by reducing the forces exerted on the driver and passengers in an automobile collision. Cars are designed with a "crumple zone" in front of the car. In the event of an impact, the passenger compartment decelerates over a distance of about 1m as the front of the car crumples. An occupant restrained by seat belts and airbags decelerate with the car. By contrast, an unrestrained occupant keeps moving forward with no loss of speed (Newton's first law!) until hitting the dashboard or windshield. These are unyielding surfaces, and the unfortunate occupant then decelerates over a distance of only about 5 mm.

Part A.
A 60 kg person is in a head-on collision. The car's speed at impact is 15 m/s. Estimate the net force on the person if he or she is wearing a seat belt and if the airbag deploys.

Part B.
Estimate the net force that ultimately stops the person if he or she is not restrained by a seat belt or airbag.

Part C
What is the force in part A in terms of the person's weight?

Part D
What is the force in part B in terms of the person's weight?

The engineer of a passenger train traveling at 25 m/ssights a freight train whose caboose is 200m ahead on the sametrack. The freight train is traveling at 15 m/s in the samedirection as the passenger train. The engineer of the passengertrain immediately applies the brakes, causing a constantacceleration of -0.100 m/s^2, while the freight train continueswith a constant speed. Take x=0 at the location of the front of thepassenger train when the engineer applies the brakes. (a) will thecows nearby witness a collision?

Do i find the acceleration of the freight train and then find thefinal velocity to find out how long it takes to stop after thebrakes are applied ? I'm stuck on how to start this question?

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