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26 Nov 2019

Question: A car in stop-and-go traffic starts at rest, movesforward 17 in 8.0 , then comes to rest again.


A) What distance does the car cover in the last 2.0 seconds of itsmotion?



B)What is the constant speed that characterizes the middle portionof its motion?


Please show each step and explain

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Related textbook solutions

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

Related questions

A car in stop-and-go traffic starts at rest, moves forward 22m in 8.0s,then comes to rest again. The velocity-versus-time plot for this car is given in the figure. What distance does the car cover in

(a) the first 4.0 seconds of this motion and

(b) the last 2.0 seconds of its motion?

(c) What is the constant speed v that characterizes the middle portion of its motion?

Q: As soon as a traffic light turns green, a car speeds up fromrestto 50 miles/hours with constant acceleration 9miles/hour*seconds.In the adjoining bike lane, a cyclist speeds upfrom rest to 20miles/hour with constant acceleration 13miles/hours*seconds. Eachvehicle maintains constant velocity afterreaching its cruisingspeed.
a) For what time interval is the bicycle ahead of the car?
b) By what maximum distance does the bicycle lead the car?

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In step 3, I do not understand where the second equation camefrombecause it is not given in the text. Can you explain how youcomeup with that equation?

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Step 2 includes the calculations in finding the time for the biketoreach the cruising speed which is 1.54 seconds.
time = (final velocity - initial velocity)/ acceleration
time = (20-0)/13
time = 1.54 seconds

Step 3 says "For the car has to overcome the bicycle both hastotravel same distance in the same time 't'.
1st equation: distance = (initial velocity*time) +(.5*accelerationof car*time squared)
distance = 0 + (.5*9mi/hs*timesquared)
distance = 4.5*time squared
2nd equation:
distance = (initial velocity of bike*time) + (.5*accelerationofcar*time of bike squared) + (final velocity of car)*(time- timeofbike)
distance = 0 + (.5*13 mi/hs*1.54seconds squared)+(20mi/h)*(t-1.54s)
distance = 20t-15.4

-- afterwards it says to take both equations and equal them toeachother to solve for time
which gives the answer where the bicycle is ahead of the car int(time) = 3.45 seconds

vf = vi + at
rx = vit + ½ at2
vf2 = vi2 +2arx
rx = ½ (vi + vf)t

4. A sailboat is moving across the water at 3.0 m/s. A gust of windfills its sails and it accelerates at a constant 2.0 m/s2. At thesame instant, a motorboat at rest starts its engines andaccelerates at 4.0 m/s2. After 3.0 seconds have elapsed, find thevelocity of (a) the sailboat, and (b) the motorboat.



7. A rail gun uses electromagnetic energy to accelerate objectsquickly over a short distance. In an experiment, a 2.00 kgprojectile remains on the rails of the gun for only 2.10x10-2 s,but in that time it goes from rest to a velocity of 4.00×103 m/s.What is the average acceleration of the projectile?



12. A space shuttle sits on the launch pad for 2.0 minutes, andthen goes from rest to 4600 m/s in 8.0 minutes. Treat its motion asstraight-line motion. What is the average acceleration of theshuttle (a) during the first 2.0 minutes, (b) during the 8.0minutes the shuttle moves, and (c) during the entire 10 minuteperiod? (be careful with min and seconds)



19. The United States and South Korean soccer teams are playing inthe first round of the World Cup. An American kicks the ball,giving it an initial velocity of 3.6 m/s. The ball rolls a distanceof 5.0 m and is then intercepted by a South Korean player. If theball accelerates at -0.50 m/s2 while rolling along the grass, findits velocity at the time of interception.




23. The city is trying to figure out how long the traffic lightshould stay yellow at an intersection. The speed limit on the roadis 45.0 km/h and the intersection is 23.0 m wide. A car istraveling at the speed limit in the positive direction and canbrake with an acceleration of -5.20 m/s2. (a) If the car is to stopon the white line, before entering the intersection, what is theminimum distance from the line at which the driver must apply thebrakes?



**(b) How long should the traffic light stay yellow so that if thecar is just closer than that minimum distance when the light turnsyellow, it can safely cross the intersection without having tospeed up?

I no this is alot of questions but im having trouble answeringthese! So please help me..

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