Physics: Displacement
Physics

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A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 15.0 min at 85.0 km/h, 20.0 min at 60.0 km/h, and 45.0min at 45.0 km/h and spends 55.0 min eating lunch and buying gas.
a)Determine avg speed for trip.
b)Determine the distance between the initial and final cities along the route.
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Convert all the minutes that he traveled in to hours by dividing them by 60
When drove at 85kph for 15 minutes...so that in a a quarter an hour. The total distance he covered was 85x1/4=21.25 km
when he drove at 60kph for 20 minutes he covered a distance of 60x1/3=20km
when he drove at 45kph for 45 minutes he covered a distance of 45x3/4 =33.75km
75 kmHe spent how many minutes in total? 15+20+45+55=135 minutes
Convert the minutes unto hours by dividing them by 60
135/60=2.25 hours
Remember, speed=distance/time
so the average speed will be the total distance covered divided by the time taken to cover it
75/2.25=33.33 km
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