Sample Exercise: Rowing With and Against the Current
Two rowers, Derek and Teresa, are in a boat. Derek can row at a steady speed of 3.8 MPH, and Teresa can row at a steady speed of 4.6 MPH. If the water in the stream is moving at a speed, $v_{we}$ , of 4.0 MPH relative to the bank, determine the velocity of the boat relative to the earth (or bank), $v_{be}$ , when

Question

Sample Exercise: Rowing With and Against the Current
Two rowers, Derek and Teresa, are in a boat. Derek can row at a steady speed of 3.8 MPH, and Teresa can row at a steady speed of 4.6 MPH. If the water in the stream is moving at a speed, [latex]v_{we}[/latex], of 4.0 MPH relative to the bank, determine the velocity of the boat relative to the earth (or bank), [latex]v_{be}[/latex], when

a) Derek rows against the current,

For Derek, [latex]v_{bw}= 3.8 MPH[/latex]

[latex]v_{bw}= 3.8 MPH[/latex]

[latex]v_{we}= -4.0 MPH[/latex]

[latex]v_{be}= ?[/latex]

b) when Teresa rows against the current,

For Teresa, [latex]v_{bw}= 4.6 MPH[/latex]

[latex]v_{bw}= 4.6 MPH[/latex]

[latex]v_{we}= -4.0 MPH[/latex]

[latex]v_{be}= ?[/latex]

and c) when Derek rows with the current.

For Derek, [latex]v_{bw}= -3.8 MPH[/latex] (downstream)

[latex]v_{bw}= -3.8 MPH[/latex]

[latex]v_{we}= -4.0 MPH[/latex]

[latex]v_{be}= ?[/latex]

Accepted Answer

We will assume that the direction of the current, downstream, is negative. Therefore, if a velocity is positive the movement is upstream (or against the current), and if it is negative the movement is downstream (or with the
current).

a. [latex]v_{be}= v_{bw} + v_{we}[/latex]

[latex]v_{be}= 3.8 + (-4.0)[/latex]

[latex]v_{be}= -0.2 [/latex] MPH (downstream)

b. [latex]v_{be}= v_{bw} + v_{we}[/latex]

[latex]v_{be}= 4.6 + (-4.0)[/latex]

[latex]v_{be}= +0.6[/latex] MPH (upstream)

c. [latex]v_{be}= v_{bw} + v_{we}[/latex]

[latex]v_{be}= -3.8 + (-4.0)[/latex]

[latex]v_{be}= -7.8[/latex] MPH (downstream)

Question 20.1: Sample Exercise: Rowing With and Against the Current Two row...

Related Answered Questions

Sample Exercise: Adding Energy Adds Mass A Bunsen burner adds 1000 J of heat energy to a beaker of water. What is the increase in the mass of the water? ...

Verified Answer:

Sample Exercise: A Contraction in Length A spaceship traveling at the velocity of 1.8 × 10^8 m/s (0.6c) covers a distance of 900 km as measured by an observer on the Earth. a. What is the distance traveled in this time as measured by the pilot of the spaceship? b. How much time does it take to ...

Verified Answer: