Low Air in Tires: Impact on Fuel Efficiency

[ashishsinghal]

Homework Statement

Why does a car uses more fuel with lesser air in tyres?

Homework Equations

Work done =F.d

The Attempt at a Solution

According to me Friction does no work in rolling if the tyre is purely circular. But when tyes are deflated then they are not circular. Due to this friction does negative work on the wheels. Due to this kinetic energy of the car decreases and hence same velocity needs more fuel. Is that correct? Also is there anything else to be considered.

 

[Andrew Mason]

Homework Statement

Why does a car uses more fuel with lesser air in tyres?

Homework Equations

Work done =F.d

The Attempt at a Solution

According to me Friction does no work in rolling if the tyre is purely circular. But when tyes are deflated then they are not circular. Due to this friction does negative work on the wheels. Due to this kinetic energy of the car decreases and hence same velocity needs more fuel. Is that correct? Also is there anything else to be considered.

I don't follow your reasoning. Why would friction do negative work on the tires simply because the tires are not round?

Think of the tire wall. What happens to the tire during a rotation when it is properly inflated? Does the tire wall change shape? How about when it is under-inflated? Does it take energy to change the shape of the tire?

AM

 

[ashishsinghal]

My point is: When considering a rolling circular disc, friction acts on the lowermost point. Let the displacement be dx and force be F. Then work done will be F.dx . After that the particle will not be in contact and hence friction force will not act. So work will be zero.

For a deflated tyre the particle will remain in contact for finite x and hence friction will do work on it.

 

[PhanthomJay]

My point is: When considering a rolling circular disc, friction acts on the lowermost point. Let the displacement be dx and force be F. Then work done will be F.dx . After that the particle will not be in contact and hence friction force will not act. So work will be zero.

For a deflated tyre the particle will remain in contact for finite x and hence friction will do work on it.

The resistance to motion of a deflated tyre that is not slipping with respect to the ground is neither due to static nor dynamic (sliding) friction, but rather, it is due to rolling friction, which is primarily caused by energy losses mostly in the form of heat when the tyre deforms and rebounds to its original shape. This is the energy loss referred to by Mr. Mason in the above post. This deformation is much greater than it would be for a properly inflated tyre, and hence, more energy losses.

 

[rwisz]

I can provide a more in-depth explanation for the impact of low air in tires on fuel efficiency. When a car is in motion, the tires are constantly rotating and making contact with the road. This contact creates friction, which is necessary for the car to move. However, when the tires are underinflated, the surface area in contact with the road increases, leading to higher friction.

This increased friction requires the engine to work harder to maintain the same speed, resulting in a higher fuel consumption. Additionally, when the tires are not properly inflated, the car's weight is not evenly distributed across the tires, causing uneven rolling resistance. This leads to the engine having to work even harder to maintain a consistent speed, further increasing fuel consumption.

Moreover, low air in tires can also lead to decreased tire pressure, which can result in a decrease in tire diameter. This decrease in diameter leads to a decrease in the number of rotations per mile, causing the speedometer to read a lower speed than the actual speed of the car. As a result, the driver may unknowingly increase their speed, leading to an increase in fuel consumption.

In summary, low air in tires leads to increased friction, uneven rolling resistance, and inaccurate speed readings, all of which contribute to a decrease in fuel efficiency. Therefore, it is important to regularly check and maintain proper tire pressure to optimize fuel efficiency and reduce the environmental impact of driving.