Mechanics> A boat takes 2 hours to travel 8 km and b...

A boat takes 2 hours to travel 8 km and back in still water .If the velocity of water is 4m/hr ,the time taken for going upstream 8km and coming back is.?Thanks in advance :)

Khushi goyal , 7 Years ago

Grade 11

5 Answers

Ritha

Last Activity: 7 Years ago

From the first condition we can determine the speed of boat....v = 8km / 2hr = 4km/h

...the velocity of water is 0.004km/h

During upstream motion the net velocity would be 4-0.004 = 3.996km/h

So time taken (t) = distance/speed=8 / 3.996 = 2.002hr

During downstream motion net velocity will be 4 + 0.004 = 4.004km/h

=> t = 8 / 4.004 = 1.998hr

Aanshi

Last Activity: 7 Years ago

Time=distance/velocityVbr= 8km/hVrg=4km/hLet t1 and t2 be the time taken by boat to travel in upstream and downstream respectivelyUpstream=8-4=4Downstream=8+4=12T1=8/4=2hrT2=8/12=2/3Total time=2+2/3=2 hr and 40 mins

Approved

Surendra

Last Activity: 6 Years ago

time = distance/velocity
when in the direction of current velocity = 8+4= 12
t1= 8/12 = 2/3 hr
when against the current velocity 8-4 = 4
t2= 8/4 = 2 hr.
total time = 2+ 2/3 = 8/3 hrs. = 2 hrs&40 minutes

Vanshika

Last Activity: 6 Years ago

Here the speed of water is still. So, they will have equal velocity and equal time taken.

☆ Total time = 2 hrs

Time for upstream = 1 hr

downstream = 1 hr

☆ their velocity is 8 kmph each.

So, new downstream velocity will be (8+4) = 12 kmph

new upstream velocity will be (8-4) = 4 kmph

TIME TAKEN = DISTANCE / VELOCITY

(distance is 8 km in both cases )

=( 8/12 + 8/4 ) hours

=( 2/3 + 2 ) hrs

= 160 mins = 2 hr 40 mins

Kushagra Madhukar

Last Activity: 4 Years ago

Dear student,

Please find the solution to your problem below.

Time = distance/velocity

when in the direction of current, relative velocity with respect to ground = 8+4= 12
t₁= 8/12 = 2/3 hr
when against the current, velocity w.r.t ground = 8-4 = 4
t₂= 8/4 = 2 hr.
total time = 2+ 2/3 = 8/3 hrs. = 2 hrs&40 minutes

Hope it helps.

Thanks and regards,

Kushagra