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tajivie
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Homework Statement
Two boats, A and B, travel with a velocity of 4.90m/s across a river with a width of 72.9m. The river flows with a velocity of 2.50m/s. Boat A travels the shortest distance and boat B travels the shortest time. If both start at the same time, how much time will they take to cross the river?
Homework Equations
There are no equations given, but I was able to use this...
Δd/v(boats)+v(river)=shortest time
Δd/v(boats)-v(river)=shortest distance
The Attempt at a Solution
Boat A: (Shortest Distance)
72.0m/(4.9m/s-2.5m/s)=72/2.4=30s
Boat B:(Shortest Time)
72m/(4.9m/s+2.5m/s)=72/7.4=9.7s≈10.0s
My Answer: Boat A can make it in 30s while Boat B can make it in 10s. I did this on a test and missed all of the points possible. Can anyone please help me find my error ansd reach a resonable answer? Thank You!