Calculating River Flow Using Reference Frames

In summary, the boat takes 3.20 hours to travel 10.0 km down the river and 6.10 hours to return. To find the velocity of the river, use reference frames and set up two equations: vb + vw = downstream velocity and vb - vw = upstream velocity. Solve for the velocity of the boat by adding the given velocities and dividing by two. Then, solve for the velocity of the water using either of the equations.
  • #1
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A boat takes 3.20 hours to travel 10.0 km down a river, then 6.10 hours to return. How fast is the river flowing?

can someone give some suggestions as to how to do this? I am guessing you use reference frames. thanks in advance.
 
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  • #2
Use the data you have to find the velocity each way, then you should be able to finish it from there.
 
  • #3
what am i supposed to do with the velocities? i tried taking the difference of the velocities divided by the difference in time but that was wrong. am i supposed to find the velocity of the boat itself and find it relative to the actual rate the boat traveled?
 
  • #4
Remember that when the boat is traveling with the current, the velocity of the boat relative to the water plus the velocity of the water equal its total velocity relative to the shore (you were right, this is about reference frames). On the return trip...you guessed it, the velocities are subtracted. Can you set up an equation with one variable to solve for?
 
  • #5
ahh yes i got it now
basically set up two equations vb + vw = downstream velocity and vb - vw = upstream velocity. find vb (velocity of boat) by adding both given velocities and divide by two. then solve for vw (velocity of water) using either of the equations.
 
  • #6
:smile: :smile: :smile:
 

1. What is the definition of relative motion?

Relative motion refers to the movement of an object with respect to another object. It takes into account the perspective of the observer and how the motion of one object appears in relation to the other object.

2. How do you solve a relative motion problem?

To solve a relative motion problem, you need to first identify the two objects in motion and their respective velocities. Then, determine the reference frame of the observer and use vector addition or subtraction to find the relative velocity between the two objects.

3. What is the difference between relative motion and absolute motion?

Relative motion takes into account the perspective of the observer and how the motion of one object appears in relation to another object, while absolute motion refers to the exact position and velocity of an object without considering any external reference frames.

4. Can relative motion be applied to both linear and circular motion?

Yes, relative motion can be applied to both linear and circular motion. In linear motion, the relative velocity between two objects is determined using vector addition or subtraction. In circular motion, the relative angular velocity is found using trigonometric functions.

5. How is relative motion used in real-life applications?

Relative motion is used in various real-life applications, such as navigation systems, air traffic control, and understanding the motion of celestial bodies. It also plays a crucial role in understanding the behavior of fluids and the physics of collisions in sports and transportation industries.

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