Force due to wind and rolling friction on van

In summary, the conversation is about finding the size of the force due to wind and rolling friction for a minivan coasting on neutral along a straight, level road, loaded with windsurfing equipment and towing a boat. The total mass of the minivan is 2500 kg and it is traveling at a speed of 44.17 mph. The equation F=ma is used to find the force, but the issue is how to find the instantaneous acceleration at a specific point on the graph. The solution is to draw a tangent line at that point and use the slope of the line to find the derivative, which is the instantaneous acceleration. The correct answer for this problem is 764 N.
  • #1
fruitl00p
94
0

Homework Statement


The graph shows the speed as a function of time for a minivan, coasting on neutral along a straight, level road, loaded with windsurfing equipment and towing a boat. The total mass is 2500 kg, weight= 5512lbs. Find the size of the force due to wind and rolling friction when the van speed is 44.17 mph. (1 mph=0.447m/s)


Homework Equations


F=ma


The Attempt at a Solution


I don't think anyone needs to see the graph to understand my problem. Well I hope.

I understand that a= delta v/delta t. But whenever I use the equation I get an acceleration that does not work. Then I thought that since the equation wants the force at 44.17 mph, that I need to find the instantaneous acceleration.

That's my problem: I don't know how to get the instantaneous acceleration. At 44.17 mph the time is at 19 s. Should I create a derivative. If so, how do I go about it?

The answer for this problem is 764 N

Please tell me why my approach is incorrect.
 
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  • #2
fruitl00p said:
That's my problem: I don't know how to get the instantaneous acceleration. At 44.17 mph the time is at 19 s. Should I create a derivative. If so, how do I go about it?


That's right, calculate the instantaneous acceleration by finding the derivative of the graph at the given time. You must be able to find a way to do that (draw a tangtent).

Good luck!
 
  • #3
da_willem, that is my problem. I do not know how to find the derivative of the graph. If I am given a derivative, I can do it; but to look at a graph and create one I just don't know.
 
  • #4
In the graph you draw a line tangential to a point where you want to know the derivative (a 'tangent line'). The derivative in that point is now the 'slope' of this line, i.e. a vertical interval ([itex] \Delta v[/tex]) divided by a corresponding horizontal interval ([itex] \Delta t[/tex]): ([itex] \Delta v /\Delta t[/tex]).
 
  • #5
I got it now. Thank you da_willem
 

1. What is the force due to wind on a van?

The force due to wind on a van refers to the external pressure that is exerted on the van as it moves through the air. This force is caused by the resistance of the air to the van's forward motion and can vary depending on factors such as the speed and direction of the wind, the shape and size of the van, and the surface properties of the van's exterior.

2. How does wind speed affect the force on a van?

The force due to wind on a van increases as wind speed increases. This is because the faster the wind is moving, the greater the pressure it exerts on the van's surface. Therefore, a van traveling in higher wind speeds will experience a stronger force due to wind compared to one traveling in lower wind speeds.

3. What is rolling friction and how does it affect a van?

Rolling friction is the resistance force that occurs when a van is in motion and its wheels are in contact with the ground. This friction is caused by the deformation of the van's tires and the roughness of the road surface. It acts in the opposite direction of the van's motion and can decrease its speed and efficiency.

4. How does the weight of a van affect the force due to rolling friction?

The weight of a van has a direct impact on the force due to rolling friction. The heavier the van, the greater the force of gravity pulling it down onto the road surface, which in turn increases the amount of friction between the tires and the road. This means that a heavier van will experience a greater force due to rolling friction compared to a lighter van.

5. Can the force due to wind and rolling friction be reduced?

Yes, the force due to wind and rolling friction can be reduced. For wind resistance, this can be achieved by designing the van with a more aerodynamic shape and by reducing its speed. For rolling friction, using tires with less rolling resistance and maintaining proper tire pressure can help reduce the force. Additionally, keeping the van's weight to a minimum can also decrease the force due to both wind and rolling friction.

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