*Please show work* 1.Dr. Drew was driving his Porsche at 200 m/sec, but then com

Question

*Please show work*

1.Dr. Drew was driving his Porsche at 200 m/sec, but then comes to a complete stop after driving 300 meters. How long did it in seconds take for him to stop?

2.) When you normally drive the freeway between Sacramento and San Francisco at an average speed of 115 km/hr (71.5 mph ), the trip takes 1.00 hr and 13.0 min . On a Friday afternoon, however, heavy traffic slows you down to an average of 100 km/hr (62.1 mph ) for the same distance. How much longer does the trip take on Friday than on the other days?

3.) While driving on the freeway at 110 km/h, you pass a truck whose total length you estimate at 25 m.

a.) If it takes you, in the driver’s seat, 5.6 s to pass from the rear of the truck to its front, what is the truck’s speed relative to the road?

b.) How far does the truck travel while you’re passing it?

Explanation / Answer

1)

initial velocity vox = 200 m/sec

final velocity vx = 0

distance x = 300 m

distance = average velocity*t

x = (vox + vx)*t/2

300 = (200+0)*t/2

time t = 3 s

==========================

2)

distance between Sacramento and San Francisco s = v1*t1

v1 = 115 km/hr

t1 = 1 hr 13 min = 60 + 13 = 73 min

time taken on friday t2 = s/v2 = (v1/v2)*t1

t2 = (115/100)*73 = 83.95 min

the trip takes 83.95 - 73 = 10.95 min more on Friday than on the other days

-------------

3)

distance travelled by you x1 = v1*t

distance traveled by truck x2 = v2*t

x1 - x2 = 25

(v1-v2)*t = 25

v1 = 110 km/h = 110*(5/18) = 30.6 m/s

(30.6-v2)*5.6 = 25

v2 = 26.14 m/s       <<<------ANSWER

(b)

distance traveled by truckx2 = 26.14*5.6 = 146.4 m <<<------ANSWER

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