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27 Nov 2019

Driving home from school one day, you spot a ball rolling out into the street. You brake for 1.20 seconds, slowing your 950-kg car from 16 m/s to 9.50 m/s. (A) What was the average force exerted on your car during brake? (B) How far did you travel during brake?

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Beverley Smith
Beverley SmithLv2
21 Apr 2020

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Related textbook solutions

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

Related questions

A straight road is used to test the driver's reaction time and thecar's acceleration. The driver is instructed to immediately pushthe brake pedal
when the car is just passing a white marker post and to keeppressing the brake pedal until the car comes to a complete stop.The distance from the car
to the white post is then measured. The driver's reaction time isthe time between when the car just passes the post and when thebrake pedal is pushed,
The driver's reaction time and the car's acceleration were the samefor both runs.
The 1500 kg car is 4.7 m long. The 50 kg driver is 1.7 mtall.

For the first run, the car was moving at 26.4 when it passed thewhite post and stopped 95.1 m from the post.
For the second run, the car was moving at 45.4 when it passed thewhite post and stopped 251.6 m from the post.


a) What was the magnitude of the car's acceleration after the brakepedal was pushed?

m/s^2

b) What was the driver's reaction time?

s

c) For the first run, how much time did it take for the car to stopafter the brake pedal was pushed?

s

d) For the first run, how far did past the white post did thedriver push the brake pedal?

m

e) For the first run, how much further did the car travel after thebrake pedal was pushed?

m

p.s can you please show me the formulas on how the answers wereobtain and how they were used? thank you SOME ONE ELSE DID THEPROBLEM BUT GOT A, C,E RITE BUT GOT B AND D WRONG A=4.945,B=.94C=5.334 D24.684 E=70.416 CAN YOU PLEASE BE CLEAR ON HOW TO COME OUTWITH THE ANSWER PLEASE

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?

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?

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