# How Do Tractive Forces and Rolling Resistance Affect a Car Wheel's Motion?

• cb951303
In summary, the tire is powered by a motor of torque T and the weight is W. The static friction force is Fs and the tire is moving upwards in a constant speed of V. The force needed to move the tire upwards is F = F_s + F_{rr} + W.sin(\alpha).
cb951303
Diagram = http://i.imgur.com/LaUO4.jpg

The tire is powered by a motor of torque T. It's weight is W and the static friction force is Fs. Consider that the tire is moving upwards in a constant speed of V.

I would like to understand the relations between forces on a model like above.
Also how can I show the rolling resistance? What's the direction?
For example what would be the value of Fs?

What resources/books can you recommend to better understand this?

Thank you

Ok from what i understand rolling resistance creates a torque opposite to the motor but where from the force is applied? How can i include in my calculations?

See http://hpwizard.com/car-performance.html" (at the bottom of the page, Theory »» Longitudinal acceleration)

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Ok I think I cracked it.
According to wiki page rolling resistance is applied in the reverse direction of the motion from the center of the wheel (somehow I missed it the first time sorry)

Since there is no acceleration the overall force should be 0 thus I can write this equation

$F_s = F_{rr} + W.sin(\alpha)$ where $F_s = T/r$ and $F_{rr} = W.cos(\alpha).C_{rr}$ so the equation becomes:

$T/r = W.cos(\alpha).C_{rr} + W.sin(\alpha)$

Am I on the right track here?

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How would I have to change the above equation if let's say there is an obstacle in front of the wheel by the dimensions LxL like in below

thank you

Ok I now know that the above diagram and formula is false.
The force needed to move the tire is equal to the static friction between the tire and the road right. So $F_s = W.cos(\alpha).\mu_s$
But there is also $W.sin(\alpha)$ and $F_{rr}$ working in the opposite direction of $F_s$ so the force needed to move the tire upwards is $F = F_s + F_{rr} + W.sin(\alpha)$ am I correct? anyone know any books that explains the tractive forces and rolling resistance on a car wheel?
Or can you at least provide me with a free body diagram of a car wheel at constant speed?

thank you

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## 1. What is the physics behind a powered tire?

The physics behind a powered tire involves the principles of motion and energy. When a tire rotates, it creates a force known as torque, which is responsible for the motion of the vehicle. This is possible due to the conversion of chemical energy from fuel into mechanical energy in the engine, which is then transmitted to the tires.

## 2. How does a powered tire create propulsion?

A powered tire creates propulsion through the process of friction. As the tire rotates and comes into contact with the road, the tread on the tire grips the road surface, creating friction. This friction allows the tire to push against the road and propel the vehicle forward.

## 3. What factors affect the performance of a powered tire?

Several factors can affect the performance of a powered tire, including the type and quality of the tire, the road conditions, the weight of the vehicle, and the power and torque of the engine. The air pressure in the tire also plays a significant role in its performance, as it affects the size and shape of the tire's contact patch with the road.

## 4. How does the design of a tire impact its performance?

The design of a tire can greatly impact its performance. The tread pattern, tire width, and tire composition all play a role in how the tire interacts with the road. For example, a wider tire can provide better traction, while a softer rubber composition can improve grip but may wear out faster. Additionally, the design of the tire can affect its ability to handle different road conditions, such as wet or snowy roads.

## 5. How do tires contribute to fuel efficiency?

Tires can contribute to fuel efficiency in several ways. The rolling resistance of a tire, which is the force required to keep the tire moving, can affect the amount of energy needed to power the vehicle. A tire with lower rolling resistance can improve fuel efficiency. Additionally, properly inflated tires can also improve fuel efficiency by reducing the drag and resistance on the vehicle.

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