Your Tead A person travels by car from one city to another with different consta
ID: 1879746 • Letter: Y
Question
Your Tead A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 25.0 min at 95.0 km/h, 11.0 min at 60.0 km/h, and 35.0 min at 45.0 km/h and spends 20.0 min eating lunch and buying gas (a) Determine the average speed for the trip. 64.33 differs from the correct answer by more than 10%, Double check your calculations. km/h (b) Determine the distance between the initial and final cities along the route. km and race across a 48-km-wide lake and back. Boat A goes across at 48 km/h and returns at 48 km/h. Boat B goes across at 24 km/h, and its crew, realizing how far behind it is getting, returns at 72 km/h. Turnaround times are negligible, and the boat that completes the round trip first wins. (a) Which boat wins? (Or is it a tie?) boat B b) What is the average velocity of the winning boat? Need Help?Explanation / Answer
the distance traveled in different times are
del x1 = v1 t1 = 95 km/h ( 0.41667 hours)= 39.58365 km
del x2 = v2 t2 = 60 km/h (0.18333 hours) = 10.9998 km
del x3 = v3 x3 = 45 km/h ( 0.58333 hours) = 26.24985 km
total distance = 39.58365 km+10.9998 km+26.24985 km= 76.8333 km
total time = 0.41667+0.18333+0.58333+0.33333=1.51666 h
v avg = total distance/total time = 50.65 km/h
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(2)
For boat A
the round trip
takes time
t1 = 2l/v1= 2( 48 km/48 km/h) = 2 h
For boat B it takes time
t2= l/v21+ l/v22 = 48/24+48/72 = 2.66 h
So,
the boatAcompletes the round trip first
.the distance covered by boat a is
d = v1 t1 = 48 km/hr ( 2hr) = 96 km
(b)
Average velocity is the net displacement of the boat divided by the total elapsed time. The
winning boat is back where it started, its displacement thus being zero, yielding an average
velocity of zero.
vavg = 0 km/h
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