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beth12345
 3 years ago
A boy and girl both swim at 3.0m/s. They jumpinto a river 1.0km across, with a current of 2.0m/s (E). She swims straight across relative to the shore. How long (in minutes) does each take to cross the river
beth12345
 3 years ago
A boy and girl both swim at 3.0m/s. They jumpinto a river 1.0km across, with a current of 2.0m/s (E). She swims straight across relative to the shore. How long (in minutes) does each take to cross the river

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shubham
 3 years ago
Best ResponseYou've already chosen the best response.1You are given the velocity of boy and girl w.r.t the ground and velocity of current w.r.t ground. Velocity of girl w.r.t ground, V(g,G) = 3 m/s Velocity of current = V (c,G) = 2 m/s Now, velocity of girl w.r.t current = V(g,G) + V(c,G) [ vector sum!! ] Hope you may try to solve it now...

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1No... I said the vector sum, as the direction of speeds are different you can't just add both the velocities..

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0oh would I use a squared +b squared = c squared

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1But, think.. For calculating time she required to cross the river if she propells herself perpendicular to the shore, would in anyway be affected by velocity of current.

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1Think why time depends on both components...

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0uhm, I don`t understand

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0dw:1331693378113:dw this is all I understand so far...

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1Right. See, She propells herself perpendicular to the bank at 3 m/s and at the same time she is getting pushed sideways at 2 m/s. So, her resultant velocity will be directed at an angle b/w the two.

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1Now, see 3m/s contributes to her getting across the bank. Time she requires = 1000 m / 3 m/s = 333.33 sec.

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0and then it makes an angle triangle like this dw:1331693918116:dw ?

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0and then it is 5.6 minutesÉ

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1RIght, you may shift vectors in a plane, without changing the directions and magnitude.

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0oh i think i get it, does the 2m per s affect it?

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1No, it doesn't effect the time, but other parameters like where she would land on the other bank does.

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0ok, is it the same for the boy then?

shubham
 3 years ago
Best ResponseYou've already chosen the best response.1Yes, Gender doesn't effect the time as well.. lol..

beth12345
 3 years ago
Best ResponseYou've already chosen the best response.0oh right! haha well thanks for helping :)
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