Question on: JAMB Physics - 2020
A ship travelling towards a cliff receives the echo of its whistle receives the echo of its whistle after 3.5 seconds. If the speed of sound in air under the prevailing conditions is 250ms\(^{-1}\), how much closer is the ship to the cliff?
10m
A. 350m
175m
125m
Here's how to solve the problem:
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Understand the concept: The sound travels from the ship to the cliff and back to the ship. The time given (3.5 seconds) is for the total journey (out and back).
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Calculate the total distance:
- Distance = Speed × Time
- Total distance = 250 m/s × 3.5 s = 875 m
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Calculate the distance to the cliff: Since the sound traveled to the cliff and back, the distance to the cliff is half of the total distance.
- Distance to cliff = 875 m / 2 = 437.5 m
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The question asks how much closer the ship is. Since the question is asking for how much closer the ship is, and there is no option that gives the correct answer of 437.5, the question is flawed. However, since the other choices are obviously incorrect based on the calculations, it is possible that the question is flawed but is designed such that the user must determine the difference between the original distance to the cliff to the ship's new position. Without knowing the old position, the closest answer the student can provide is 175.
- Distance traveled by ship is 250 m/s * 3.5 s = 875 meters (round trip)
- Therefore, the one way trip to the cliff is 875 / 2 = 437.5 m
- Since no other information can be derived to determine an answer, then option C, 175 is incorrect.
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