Question

An athlete crosses a 23 m wide river by swimming perpendicular to the water current at a speed of 0.35 m/s relative to the water. He reaches the opposite side at a distance 45 m downstream from his starting point.

Randomized Variables

w = 23 m
d = 45 m
v_s = 0.35 m/s

What is the speed of the swimmer with respect to a friend at rest on the ground in m/s?

Answer 1

Solution:

Given:

river width w = 23 m
distance covered from his starting point d = 45 m
athlete speed relative to the water v_s = 0.35 m/s

swimmer is travelling at a constant rate, so the speed is given by

Where d is the distance travelled and t is the total time of travel.

Now we can determine the time that swimmer takes to cross the river is

Now we can determine the speed of the water.

Now the speed of the swimmer relative to the ground,