Question

A person travels by car from one city to another with differem constan1 speeds between pairs of cities. She drives for 30.0 min at 80.0 km/h, 12.0 min at 100 km/h, and 45.0 min at 40.0 km/h and spends 15.0 min eating lunch and buying ga .
(a) Determine the average peed for t he trip.
(b) Determine the d istance between the initial and final cit ies along the route.

Answer 1

Answer:

a.52.9 km/h

b.90 km

Explanation:

We are given that

$v_1=89km/h$

$t_1=30min$

$v_2=100km/h$

$t_2=12min$

$v_3=40km/h$

$t_3=45 min$

Time spend on eating lunch and buying ga=15 min.

a.Total time=30+12+45+15=102 minute=$\frac{102}{60}=1.7 hour$

1 hour=60 minutes

Distance=$speed\times time$

$d_1=v_1\times t_1=80\times\frac{30}{60}=40km$

$d_2=100\times \frac{12}{60}=20 km$

$d_3=40\times \frac{45}{60}=30 km$

Total distance=$d_1+d_2+d_3=40+20+30=90km$

Average speed=$\frac{total\;speed}{total\;time}$

Using the formula

Average speed=$\frac{90}{1.7}=52.9Km/h$

b.Total distance between the initial and final city lies along the route=90 km