1.

A boat can go across a lake of length I and return in time To at a speed yo. On a rough day there is a uniform current moving with a speed y to help onward journey and impede the return journey. If the time taken to go across and return on the rough day is t/(t_0) then the ratio is :

Answer»

`1-(v^(2))/(v_(0)^(2))`
`(1)/(1-(v^(2))/v_(0)^(2))`
`1+(v^(2))/(v_(0)^(2))`
`(1)/(1+(v^(2))/v_(0)^(2))`

Solution :Here `t_0=(2L)/(v_0)` and `t=(l)/(v_0+v)+(l)/(v_0-v)`
or `t=((v_0-v)l+(v_0+v)l)/(v_0^2 -v^2)=(2lv_0)/(v_0^2-v^2)`
`=(1)/(1-(V^2/v_0^2))`


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