Question

Sally travels by car from one city to another. She drives for 27.0 min at 70.0 km/h, 50.0 min at 44.0 km/h, and 38.0 min at 75.0 km/h, and she spends 12.0 min eating lunch and buying gas.
(a) Determine the average speed for the trip.
km/h
(b) Determine the total distance traveled.
km

Answer 1

Answer on Question #46964, Physics, Other

Question:

Sally travels by car from one city to another. She drives for 27.0 min at 70.0 km/h, 50.0 min at 44.0 km/h, and 38.0 min at 75.0 km/h, and she spends 12.0 min eating lunch and buying gas.

(a) Determine the average speed for the trip. km/h

(b) Determine the total distance traveled. km

Answer:

Average speed equals:

$$v = \frac {S}{t}$$

where $S$ - a total distance, $t$ - a total time.

b) The total distance equals:

$$S = 27 \min \cdot 70 \frac {k m}{h} + 50 \min \cdot 44 \frac {k m}{h} + 38 \min \cdot 75 \frac {k m}{h} = 115.7 \text{ km}$$

a) The total time equals:

$$t = 27 \min + 50 \min + 38 \min + 12 \min = 127 \min = 2.12 \text{ hours}$$

Average speed equals:

$$v = \frac {115.7}{2.12} \frac {k m}{h} = 54.6 \frac {k m}{h}$$

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