Chapter 5, Problem 23A

Christopher can paddle a canoe in still water at 8 km/h. How successful will he be at canoeing upstream in a river that flows at 8 km/h?

To determine

Whether person C would be successful in canoeing upstream.

Answer to Problem 23A

He will not move at all

Explanation of Solution

Given:

Velocity of person C in still water $=v_c=8\frac{\text{km}}{\text{h}}$

Velocity of river $=v_r=-8\frac{\text{km}}{\text{h}}$

Relative velocity of person C $=\Delta v$

Formula Used:

Relative velocity A with respect to B is given as

  $v_{AB}=v_A+v_B$

  $v_A$ is velocity of A.

  $v_B$ is velocity of B.

  $v_{AB}$ is velocity of A with respect to B.

Calculation:

Relative velocity of person C with respect to river is given as

  $\begin{array}{l}{v}_{cr}=v_c+v_r\\ v_{cr}=8+(-8)\\ v_{cr}=0\frac{\text{km}}{\text{h}}\end{array}$

Conclusion:

Hence, person C does not move in any direction.