Engineering Board Exam Reviewer · Solutions to Right Triangles · hard
ECE Board November 1991: The captain of a ship views the top of a lighthouse at an angle of 60° with the horizontal at an elevation of 6 meters above sea level. Five minutes later, the same captain of the ship views the top of the same lighthouse at an angle of 30° with the horizontal. Determine the speed of the ship if the lighthouse is known to be 50 meters above sea level.
- 0.265 m/sec
- 0.155 m/sec
- 0.169 m/sec
- 0.210 m/sec
Answer
C. 0.169 m/sec
Solution
Effective height =50-6=44 m. Initial distance: d1=44/ 60° 25.4 m. Distance after 5 min: d2=44/ 30° 76.2 m. Distance traveled =d2-d1 50.8 m in 300 s, giving speed 50.8/300 0.169 m/sec.
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