Question

Sally travels by car from one city to another. She drives for 27.0 min at 66.0 km/h, 45.0 min at 35.0 km/h, and 54.0 min at 80.0 km/h, and she spends 7.0 min eating lunch and buying gas.
Determine the average speed for the trip.

Answer 1

Answer on Question #47763, Physics, Mechanics — Kinematics — Dynamics

Sally travels by car from one city to another. She drives for 27.0 min at 66.0 km/h, 45.0 min at 35.0 km/h, and 54.0 min at 80.0 km/h, and she spends 7.0 min eating lunch and buying gas. Determine the average speed for the trip.

Solution

The average speed is total distance divided by total time.

$v_{a}=\frac{v_{1}t_{1}+v_{2}t_{2}+v_{3}t_{3}}{t_{1}+t_{2}+t_{3}+t_{4}}=\frac{66\cdot 27+35\cdot 45+80\cdot 54}{27+45+54+7}\approx 57.7\,km/h$

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