Solving Boat Speed & Distance with Drag Force

In summary, the boat stops after traveling a distance of ##\sqrt{3}## meters and taking ##\frac{3}{2}## seconds.
  • #1
Macykc2
13
1

Homework Statement


A boat with initial speed vo is launched on a lake. The Boat is slowed by the water by a force F=-αeβv. Find an expression for the speed v(t), and find the time and distance for the boat to stop.

Homework Equations


Drag force F=-αeβv
alpha and beta are not specified as to what they represent.

The Attempt at a Solution


I have an attached attempted solution, I'm just kind of confused on my results, I feel like it makes sense but at the same time it doesn't. My confusion lies in that I try to imagine using my derived v(t) equation but the drag force is constantly changed based on the instantaneous velocity at any moment, the v in the force equation is what throws me off, and makes me think I need to use a different approach.
Once I found my v(t) I found time when v(t)=0, then I found velocity as a function of position to find distance when v=0.
But again, now that I look at it, the v that is apart of e should probably be 0 as well, then the positions and times won't be affected by the drag force...
 

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  • #2
Macykc2 said:

Homework Statement


A boat with initial speed vo is launched on a lake. The Boat is slowed by the water by a force F=-αeβv. Find an expression for the speed v(t), and find the time and distance for the boat to stop.

Homework Equations


Drag force F=-αeβv
alpha and beta are not specified as to what they represent.

The Attempt at a Solution


I have an attached attempted solution, I'm just kind of confused on my results, I feel like it makes sense but at the same time it doesn't. My confusion lies in that I try to imagine using my derived v(t) equation but the drag force is constantly changed based on the instantaneous velocity at any moment, the v in the force equation is what throws me off, and makes me think I need to use a different approach.
Once I found my v(t) I found time when v(t)=0, then I found velocity as a function of position to find distance when v=0.
But again, now that I look at it, the v that is apart of e should probably be 0 as well, then the positions and times won't be affected by the drag force...
Posting working as an image makes it hard to comment on individual lines. (It can also be hard to read, but yours is ok.)
Better to take the trouble to type the equations in, but if you must post images please number all the equations.

You cannot integrate a function of v just by multiplying it by t. v is a variable.
Rearrange the equation so that all the references to v are on one side and t on the other (including dv, dt).
 
  • #3
I figured that's what i had to do, I took a look at it after I posted and tried some other things including that, and although I do get results it's once again hard to see if it makes sense, as they do not specify what alpha and beta are.

Also I will try in the future to just use this site instead of a picture, I'm just not good with that math function as I've never used it.

I ended up with v(t)=##\frac{1}{β}##ln(eβvo - ##\frac{αβt}{m})## but as I said, it's hard to know if what I did is right with the lack of info.
 
  • #4
I also just noticed a very crucial mistake, this whole time I've been writing eβv as e-βv, so I need to re-do everything...
 

1. How does drag force affect boat speed and distance?

Drag force is the resistance force that acts against a moving object, such as a boat, in a fluid (e.g. water). This force increases as the speed of the boat increases, making it more difficult for the boat to move through the water. As a result, the drag force ultimately slows down the boat and reduces its overall distance traveled.

2. What factors contribute to drag force in boats?

There are several factors that contribute to drag force in boats, including the shape and size of the boat, the speed at which it is moving, and the properties of the fluid it is moving through. Other factors such as surface roughness and the presence of obstacles in the water can also affect drag force.

3. How can drag force be reduced in boats?

There are several ways to reduce drag force in boats, such as designing the boat with a streamlined shape, reducing its weight, and using materials with low drag coefficients. Additionally, maintaining a consistent and efficient speed can also help to minimize drag force.

4. How does drag force impact fuel efficiency in boats?

Drag force can significantly impact fuel efficiency in boats. As drag force increases, more energy is required to maintain the same speed, resulting in higher fuel consumption. Therefore, reducing drag force can improve fuel efficiency and save on costs.

5. Are there any mathematical equations used to calculate drag force in boats?

Yes, there are several equations used to calculate drag force in boats, such as the drag equation and the Reynolds number. These equations take into account various factors, such as the boat's speed, size, and shape, and can be used to estimate the drag force and its impact on the boat's performance.

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