# Motion Along a Straight Line: Calculate velocity of a stream

• alexsphysics
In summary, the conversation discusses the calculation of a swimmer's speed relative to the water and the bank. It is determined that the swimmer is moving at a speed of 20 km/h relative to the water and 8 km/h upstream. By subtracting the two equations, it is found that the speed of the water is 6 km/h. The conversation ends with a realization that the problem was simpler than originally thought.
alexsphysics
Homework Statement
A swimmers speed along the river is 20 km/h and upstream is 8 km/h. Calculate the velocity of the stream and the swimmers possible speed in still water
Relevant Equations
I understand what the variables are and I understand what it is asking to find, but what I'm having trouble with is putting together an equation/formula that will help solve the problem.
Not sure how to go about it

Assuming that the swimmer is swimming at the same speed relative to the water then, writing "u" for the speed of the swimmer, relative to the water and "v" for the speed of the water, then u+ v= 20 and u- v= 8. If you subtract the second equation from the first, 2v= 12 so v= 6 km/h.

alexsphysics
Why does u-v=8?

Swimming upstream the swimmer is moved backward by the current. If his speed relative to the water is u and the speed of the water is v, then his speed relative to the bank is u- v. In your first post you said "A swimmers speed along the river is 20 km/h and upstream is 8 km/h" so u- v= 8 km/h.

alexsphysics
Yes, that is much more simple that I sought out the problem to be for some reason. Thanks a lot!

## 1. What is the formula for calculating velocity of a stream?

The formula for calculating velocity of a stream is v = d/t, where v is velocity in meters per second (m/s), d is distance in meters (m), and t is time in seconds (s).

## 2. How do you measure the distance of a stream?

The distance of a stream can be measured using a measuring tape or by using a ruler to measure the distance between two points along the stream.

## 3. How do you measure the time it takes for the water to flow through a certain distance?

To measure the time it takes for water to flow through a certain distance, you can use a stopwatch or a timer. Start the timer when the water reaches the starting point and stop it when it reaches the ending point.

## 4. What are the units of velocity for a stream?

The units of velocity for a stream are meters per second (m/s).

## 5. How does the velocity of a stream affect its flow rate?

The velocity of a stream directly affects its flow rate. The higher the velocity, the faster the water is flowing, resulting in a higher flow rate. Similarly, a lower velocity will result in a slower flow rate.

• Introductory Physics Homework Help
Replies
98
Views
4K
• Introductory Physics Homework Help
Replies
25
Views
1K
• Introductory Physics Homework Help
Replies
7
Views
392
• Introductory Physics Homework Help
Replies
9
Views
673
• Introductory Physics Homework Help
Replies
8
Views
391
• Introductory Physics Homework Help
Replies
7
Views
2K
• Introductory Physics Homework Help
Replies
8
Views
2K
• Introductory Physics Homework Help
Replies
19
Views
318
• Introductory Physics Homework Help
Replies
7
Views
1K
• Introductory Physics Homework Help
Replies
11
Views
1K