Swimmer's velocity relative to the shore (vectors)

  • Thread starter ulfy01
  • Start date
  • #1
6
0

Homework Statement


A swimmer is training in a river. The current flows at 1.33 metres per second and the swimmer's speed is 2.86 metres per second relative to the water. What is the swimmer's speed relative to the shore when swimming upstream? What about downstream?

Homework Equations



Pythagoras.

The Attempt at a Solution



Here's my problem. Because we're looking at vectors, I would normally do the vector sum of both the velocities and use Pythagoras, as both given vectors are perpendicular.


Vcurrent = 1.33 m/s
Vswimmer relative to water = 2.86 m/s

So the resultant vector would be: [itex]\sqrt{}[/itex](1.332 + 2.862)

Giving 3.15 m/s, however this is wrong, as the answer given is 1.53 m/s upstream.

I'm puzzled as to how this answer was reached.
 

Answers and Replies

  • #2
1,065
10
The swimmer is not swimming across the river.
He is swimming against the current. That how normally swimmers trainned.
Now imagine you running in direction to the east at a speed 1.33 metres per second on a train with 1.33 metres per second speed heading west.
To the man on the platform seeing you not moving, but with respect of the train you are running at 1.33 metres per second in easterly direction.
 
  • #3
TSny
Homework Helper
Gold Member
13,075
3,395
Hi, ulfy01.

Note that "swimming upstream" means swimming in a direction opposite to the current, not perpendicular to the current. So, there is no right triangle here.

[oops: I'm a bit late here, sorry.]
 
  • #4
6
0
I just realized this and made a fool of myself, really. Way to overthink a problem and not read it properly. I'll go hide in a corner now. Thanks azizlwl!
 

Related Threads on Swimmer's velocity relative to the shore (vectors)

Replies
4
Views
1K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
1
Views
335
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
5
Views
5K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
4
Views
6K
Top