# Rolling Friction of Bicycle Tires

• neongoats
In summary, the question is asking for the coefficient of rolling friction for a low pressure bicycle tire that is set rolling with an initial speed of 3.30m/s. The distance traveled before the speed is reduced by half is measured for two different tire pressures, 40 psi and 105 psi. Using the equations Fx=ma and Fx=μn, and substituting n=mg, the acceleration is found to be -0.24 for both tire pressures. However, when trying to solve for the coefficient of friction μ, a negative value is obtained, which is not possible. The error may lie in the calculation of acceleration, but the overall process is correct.
neongoats

## Homework Statement

Two bicycle tires are set rolling with the same initial speed of 3.30m/s along a long, straight road, and the distance each travels before its speed is reduced by half is measured. One tire is inflated to a pressure of 40 psi and goes a distance of 17.3m ; the other is at 105 psi and goes a distance of 93.0m . Assume that the net horizontal force is due to rolling friction only and take the free-fall acceleration to be g = 9.80m/s2
What is the coefficient of rolling friction μr for the tire under low pressure?

Fx=ma
Fx=μn
n=mg
v2=v02+2a(x−x0)

## The Attempt at a Solution

First I solved for the acceleration:
1.65^2 = 3.3^2 + 2a(17.3)
a= -.24

Then I set Fx=ma and Fx=μn to be equal, and substituted n=mg in for n
ma=μmg
The masses cancel out so I get
a=μg
I tried solving for this
-.24=u(9.8)
and got -.024, but this answer was incorrect.

I feel good about this process but don't know I'm doing wrong? I found another question exactly like this on here but when I tried to do the calculations for acceleration I kept getting a different number, so I don't know if that's where my problem lies but if so I don't understand how my math is wrong.

Have a think about the concept of a negative coefficient of friction.

## 1. What is rolling friction and how does it affect bicycle tires?

Rolling friction is the resistance force that occurs when a tire rolls on a surface. It is caused by the deformation and recovery of the tire as it makes contact with the ground. This friction can affect the speed and efficiency of a bicycle as it requires energy to overcome.

## 2. How is rolling friction different from other types of friction?

Rolling friction is different from other types of friction, such as sliding or static friction, because it occurs between two surfaces that are in relative motion. In the case of bicycle tires, it is the friction between the tire and the ground as the tire rolls. Other types of friction occur between two surfaces that are either stationary or sliding against each other.

## 3. What factors can affect the rolling friction of bicycle tires?

The rolling friction of bicycle tires can be affected by several factors, including the type and tread pattern of the tire, the air pressure in the tire, the weight of the rider and the bike, the surface the tire is rolling on, and the speed at which the bike is traveling.

## 4. How can rolling friction be reduced for better performance?

To reduce rolling friction and improve the performance of bicycle tires, it is important to choose tires with a lower rolling resistance, which means they have a smoother tread pattern and are made of materials that are more flexible. Keeping tires properly inflated and using a lighter bike can also help reduce rolling friction.

## 5. Is rolling friction the only type of friction that affects bicycle tires?

No, rolling friction is not the only type of friction that affects bicycle tires. There is also air resistance, which is the force that opposes the motion of an object through the air. This can impact the speed and efficiency of a bike, especially at higher speeds. Additionally, friction between the chain and gears can also affect the performance of a bicycle.

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