Consider the street pattern shown in Fig. 2–47. Each intersection has a traffic signal, and the speed limit is 50 km/ h. Suppose you are driving from the west at the speed limit. When you are 10.0m from the first intersection, all the lights turn green. The lights are green for 13.0 s each. ( a ) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping? ( b ) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of 2.00 m/s 2 to the speed limit. Can the second car make it through all three lights without stopping? By how many seconds would it make it or not?
Consider the street pattern shown in Fig. 2–47. Each intersection has a traffic signal, and the speed limit is 50 km/ h. Suppose you are driving from the west at the speed limit. When you are 10.0m from the first intersection, all the lights turn green. The lights are green for 13.0 s each. ( a ) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping? ( b ) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of 2.00 m/s 2 to the speed limit. Can the second car make it through all three lights without stopping? By how many seconds would it make it or not?
Consider the street pattern shown in Fig. 2–47. Each intersection has a traffic signal, and the speed limit is 50 km/ h. Suppose you are driving from the west at the speed limit. When you are 10.0m from the first intersection, all the lights turn green. The lights are green for 13.0 s each. (a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping? (b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of 2.00 m/s2 to the speed limit. Can the second car make it through all three lights without stopping? By how many seconds would it make it or not?
65. Consider the street pattern shown in Fig. 2–46. Each inter-
section has a traffic signal, and the speed limit is 40 km/h.
Suppose you are driving from the west at the speed limit.
When you are 10.0 m from the first intersection, all the lights
turn green. The lights are green for 13.0 s each. (a) Calculate
the time needed to reach the third stoplight. Can you make
it through all three lights without stopping? (b) Another car
was stopped at the first light when all the lights turned green.
It can accelerate at the rate of 2.00 m/s² to the speed limit.
Can the second car make it through all three lights without
stopping? By how many seconds would it make it, or not
make it?
West O
East
0000
Speed limit
40 km/h
Your
10 m
50 m
70 m
car
15 m
15 m
15 m
FIGURE 2-46 Problem 65.
A person driving her car at 35 km/h approaches an inter-
section just as the traffic light turns yellow. She knows that
the yellow light lasts only 2.0s before turning to red, and
she is 28 m away from the near side of the intersection
(Fig. 2–49). Should she try to stop, or should she speed up
to cross the intersection before the light turns red? The
intersection is 15 m wide. Her car's maximum deceleration
is -5.8 m/s?, whereas it can accelerate from 45 km/h to
65 km/h in 6.0 s. Ignore the length of her car and her
reaction time.
– 28 m -
-15 m→
FIGURE 2-49 Problem 73.
(6) You are driving home from school steadily at 95km/h from 130km. It then begins to rain and you slow to 65km/h. You arrive home after driving 3 hours and 20 minutes.
a) How far is your hometown from school?
b) What was your average speed?
Chapter 2 Solutions
Physics for Scientists and Engineers with Modern Physics
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
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