# Work Done by Horses & Friction on Canal Boat

• tony873004
In summary, two horses pull a canal boat of mass 1.0*10^4 kg at a constant speed for a distance of 10.0 km. One horse exerts a force of 3.0*10^2 N at an angle of 20º to the canal, and the other exerts 5.0 * 10^2 N. The work done by each horse is equal to the x-component of their force multiplied by the distance. The work done by friction between the boat and the water is equal to the force of friction multiplied by the distance. The forces in the y-direction are equal and opposite to keep the boat from hitting the side of the canal. The net work done on the boat
tony873004
Gold Member
Two horses on either side of a canal pull a canal boat of mass 1.0*10^4 kg at a constant speed for a distance of 10.0 km. (Figure 7.32). One horse exerts a force of 3.0*10^2 N at an angle of 20º to the canal, and the other exerts 5.0 * 102 N. Find the work done by each horse and the work done by friction between the boat and the water.

I believe I would set it up like this:
Call the direction parallel to the canal the x axis
The work of a horse whose angle is given will be the x-component of the force * distance in meters
$$W_{horse1}=cos(20)*3*10^2N*10000m$$

The work done by the horse whose angle is not given will be the same as the first horse. Again, it will be the x-component of the force, which will be equal to Horse 1's x-component, and although the question doesn't ask for it, I could now compute Horse 2's angle.

But the work done by the friction between the boat and the water? I don't know how to solve that? What if the question said they were on ice instead of water?

The best I can come up with is
$$W_{friction}=Force_{friction} * 10000 meters$$

First, your assumption that the forces in the x-direction does not seem sound to me. On the contrary, I would expect the forces in the y-direction to be the same, but with opposite sign, and then the force in the x-direction of the second horse to be determined after that. I am missing the figure, and also I think there is a mistype, but am not sure (is the second horse actually exerting 5.0 * 10^2N?), so I may not have all necessary information.

Secondly, as to your question about the work that friction does, I hope you don't mind me asking this question: If an object is at a constant velocity for a period of time, what is the net work that has been done on it? Or better yet, if this object is at a constant velocity, what is the net force on it, and what does that mean for the work done?

Hope this helps.

To find the force of friction use

$$\Sigma F= ma$$

if the velocity is constant, then acceleration=0.

 I'm too slow...

Thanks, that does help. You're right about the typo 5.0*102 = 5.0*10^2.

Thinking about it, it does make more sense that the y-components should be equal or the boat will hit the side of the canal.

So after setting the y's equal, I have to compute both horses' x-components of force.

You're right, the constant velocity is the key. Water friction must equal the horses pulls but in the opposite direction or there'd be acceleration.

Thanks Locrain!

Gale17 said:
 I'm too slow...

## 1. What is the concept of work done by horses and friction on canal boat?

The concept of work done by horses and friction on canal boat is the amount of force required to move a canal boat along a canal. This involves the work done by the horses pulling the boat, as well as the work done by the friction of the water against the boat's hull.

## 2. How do horses contribute to the work done on a canal boat?

Horses contribute to the work done on a canal boat by pulling the boat along the canal. This requires a certain amount of force, which is dependent on the weight of the boat and the resistance of the water. The more horses pulling the boat, the more work can be done in a shorter amount of time.

## 3. How does friction affect the work done on a canal boat?

Friction plays a significant role in the work done on a canal boat. As the boat moves through the water, it experiences resistance due to the friction between the water and the boat's hull. This resistance must be overcome by the work done by the horses pulling the boat.

## 4. Is the work done by horses and friction on a canal boat a constant value?

No, the work done by horses and friction on a canal boat is not a constant value. It can vary depending on various factors such as the weight of the boat, the number of horses pulling the boat, the speed of the boat, and the condition of the canal's water. Friction can also vary depending on the shape and material of the boat's hull.

## 5. How can the work done by horses and friction on a canal boat be minimized?

The work done by horses and friction on a canal boat can be minimized by reducing the weight of the boat, using a more streamlined and smoother hull, and ensuring that the canal's water is free of debris and obstacles. Additionally, using a larger number of horses or increasing their pulling strength can also help to minimize the work done on the canal boat.

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