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Difficulty: MediumThe Earth as a Planet and Earth Movements

City A is located at longitude 25∘W25^\circ\text{W} and City B is located at longitude 65∘E65^\circ\text{E}. Calculate the difference in local solar time between the two cities in hours.

Answer: 6 hours

Answer

The time difference between City A and City B is 6 hours.
Because City A (25∘W25^\circ\text{W}) and City B (65∘E65^\circ\text{E}) lie in opposite hemispheres relative to the Greenwich Meridian (0∘0^\circ), the total longitudinal difference between them is the sum of their absolute longitudes (25∘+65∘=90∘25^\circ + 65^\circ = 90^\circ). Given that Earth rotates 15∘15^\circ of longitude every hour (360∘/24 hours360^\circ / 24\text{ hours}), dividing 90∘90^\circ by 15∘/hour15^\circ\text{/hour} gives a total time difference of 6 hours.

Step-by-Step Solution

1
Calculate the total angular distance between the two longitudes.
25∘W+65∘E=90∘25^\circ\text{W} + 65^\circ\text{E} = 90^\circ
Because the two locations are in different hemispheres (West and East), their longitudinal values must be added to find the total separation across the Prime Meridian.
2
Convert longitudinal degrees into time difference.
90∘/15∘ per hour=6 hours90^\circ / 15^\circ\text{ per hour} = 6\text{ hours}
Earth completes one full rotation of 360∘360^\circ in 24 hours, which corresponds to an angular velocity of 15∘15^\circ per hour.

Key Concept

Calculating time difference from longitudinal distance across hemispheres.
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Topics

The Earth as a Planet and Earth Movements

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