Engineering Board Exam Reviewer · Related Rates (Time Rates) · medium
A car travels north at 50 kph and another travels west from the same intersection at 30 kph, both starting at the same time. Find the rate at which the distance between them is changing after 2 hours.
- 58.31 kph
- 80 kph
- 20 kph
- 40 kph
Answer
A. 58.31 kph
Solution
Since both move at constant speed in perpendicular directions from the same point, the separation rate is constant: sqrt(502+302)=sqrt(2500+900)=sqrt(3400) 58.31 kph.
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