Prove: Swimmer's Time in Flowing River = Time in Still Water

In summary, the problem states that a swimmer crosses a river of width d in time t1 and takes the same amount of time t2 to cover the same distance up and down the stream. If t3 is the time taken to swim a distance of 2d in still water, it must be proven that t1 squared is equal to t2 times t3. To solve this problem, one must use the formulas for t1, t2, and t3 in terms of d, u, and v and manipulate them to eliminate u and v.
  • #1
riddhish
6
0
A swimmer crosses a flowing river of width d to and fro in time t1. The time taken to cover the same distance up and down the stream is t2. If t3 is the time the swimmer would take to swim a distance 2d in still water, then prove that t1 square = t2t3.
 
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  • #2
Yes, that's a really great problem! What really great attempts to solve it have you made?

I would let u be the speed of the swimmer in still water, v be the speed of the river. Then write formulas for t1, t2, t3 in terms of d, u, and v. Since there is no u or v given in the problem, you will want to manipulate the equations to eliminate those.
 
  • #3
riddhish said:
A swimmer crosses a flowing river of width d to and fro in time t1. The time taken to cover the same distance up and down the stream is t2. If t3 is the time the swimmer would take to swim a distance 2d in still water, then prove that t1 square = t2t3.

Odd that it take the same time to swim upstream and down...
 
  • #4
Good point but I suspect what was meant was that the total time to swim a distance equal to the width of the river upstream and then the same distance back downstream was t2.
 

FAQ: Prove: Swimmer's Time in Flowing River = Time in Still Water

What is the equation for proving that a swimmer's time in a flowing river is equal to their time in still water?

The equation for proving that a swimmer's time in a flowing river is equal to their time in still water is: tr = ts + d/v, where tr is the swimmer's time in the river, ts is their time in still water, d is the distance traveled, and v is the velocity of the river's flow.

How is this equation derived?

This equation is derived from the principle of relative velocity, which states that the velocity of an object relative to a moving reference frame is equal to the velocity of the object in the stationary reference frame plus the velocity of the reference frame. In this case, the swimmer's velocity in the river is equal to their velocity in still water plus the velocity of the river's flow.

What assumptions are made in this equation?

The equation assumes that the swimmer's velocity remains constant throughout the entire journey, that the swimmer is swimming in a straight line, and that the river's flow is constant and not affected by external factors such as wind or currents.

Are there any limitations to this equation?

Yes, there are limitations to this equation. It does not take into account the effects of turbulence or eddies in the river's flow, which can impact a swimmer's time. It also assumes that the swimmer's speed is equal to the velocity of the river's flow, which may not always be the case.

How can this equation be tested and verified?

This equation can be tested and verified through experiments in controlled environments. A swimmer can be timed in a still pool and then timed again in a river with known velocity and distance. The results can then be compared to see if they align with the predicted time based on the equation. Additionally, the equation can also be tested using mathematical models and simulations.

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