Calculate Force of Bike Tires with Brakes

• Vyce
In summary: It's really appreciated.In summary, a group of friends are trying to determine the force exerted on a bike's tires by its brakes. The given information includes a horizontal road, the mass of the bike and rider, initial speed, and the maximum speed before the brakes are applied. They are also given a tape measure. The group is having trouble figuring out the problem and feels overwhelmed. However, they are advised to use the work-energy theorem and the motion equation to solve for the force. The group is also reminded that the max speed is given and not to be calculated. The presence of static friction between the tires and road is also mentioned, as this needs to be taken into consideration when calculating the force.
Vyce

You and a bunch of your friends are trying to figure out what the force exerced on your bike's tires are by your brakes.
Here are the things that you have to help you figure out this problem:
-You know your own, and your bike's mass (the mass is what you decide)
-You know your initial speed (None was given)
-The final speed before you slam on your breaks is at the max before the bike would slide (meaning you are not permitted to slide at all)
-You are given a tape measure.

This is all the info I have, and trying to figure out this problem is being difficult. :/

Maybe I'm over thinking things? I feel dumb. >.>

Edit: I have no calculations already done because I do not know where to start.

Last edited:
Vyce said:
You and a bunch of your friends are trying to figure out what the force exerced on your bike's tires are by your brakes.
Here are the things that you have to help you figure out this problem:
-You know your own, and your bike's mass (the mass is what you decide)
-You know your initial speed (None was given)
-The final speed before you slam on your breaks is at the max before the bike would slide (meaning you are not permitted to slide at all)
-You are given a tape measure.

This is all the info I have, and trying to figure out this problem is being difficult. :/

Maybe I'm over thinking things? I feel dumb. >.>
Don't feel dumb. Are you familiar with the work-energy theorem, or the motion equation that relates distance, speed, and accelertaion?

So, you are supposed to derive the algebraic formula for the force? What does each part tell you?

-No extra forces to consider
-You know the inertia
-You know the intial speed
-You know that the static friction between the tire and the road is always the case
-You can determine the distance traveled with some intial velocity and some acceleration from the breaking force

Piece them all together, or if this is the part you are lost at then which piece of the overall puzzle gives you the most trouble?

Don't feel dumb. Are you familiar with the work-energy theorem, or the motion equation that relates distance, speed, and accelertaion?

I know a few work-energy formulas. (Sorry if this is incorrect, but I study in French ) :

Potential Energy and Ec (don't know the name in english)...

Ec1 + Ep1 = Ec2 + Ep2

1/2mv1^2 + mgh1 = 1/2mv2^2+mgh2
I know W = F*D or W=deltaEc= 1/2m(V2^2 - v1^2)
Is that the work-energy theorem you're talking about? Hmm, maybe if I find work then use the basic formula W=F*D, and use a distance that I choose?

But then I still wouldn't know what the max speed is before I would slide. Unless there's a formula for that, or I just don't know, plain and simple. :s

Mindscrape said:
Piece them all together, or if this is the part you are lost at then which piece of the overall puzzle gives you the most trouble?

I guess it's the part where I have to figure out what the max speed is before I would slide.

You know that between the tires and road, static friction must always exist (or else the tires slide). I think that you are supposed to just make some relation yourself that there is limiting force when the kinetic friction of the tires overcomes the static friction of the tires. You're right though, you aren't really given much to work with.

Alright then, thanks. :)

Vyce said:
I guess it's the part where I have to figure out what the max speed is before I would slide.
No, they don't want you to figure out the max speed, you assume it is given. The reason why the sliding is mentioned is that as Mindscrape noted, you don't want kinetic friction of sliding, which will slow the car, to overtake the static friction between wheel and road which is driving the car forward. Or else the force required to stop the car would be partly contributed to by the sliding before the brakes take over. Bottom line is that your work energy theorem work = F.d = delta Ec looks good en francais, but don't forget that v1 is just a given v_max, and v2 is 0! (work comes out negative).

PhanthomJay said:
No, they don't want you to figure out the max speed, you assume it is given. The reason why the sliding is mentioned is that as Mindscrape noted, you don't want kinetic friction of sliding, which will slow the car, to overtake the static friction between wheel and road which is driving the car forward. Or else the force required to stop the car would be partly contributed to by the sliding before the brakes take over. Bottom line is that your work energy theorem work = F.d = delta Ec looks good en francais, but don't forget that v1 is just a given v_max, and v2 is 0! (work comes out negative).

This also helps out a lot! I thank you both for taking the time to help me out.

1. How do I calculate the force of bike tires with brakes?

The force of bike tires with brakes can be calculated using the formula F = μmg + μma, where F is the force, μ is the coefficient of friction, m is the mass of the bike and rider, g is the acceleration due to gravity, and a is the deceleration caused by the brakes.

2. What is the coefficient of friction for bike tires?

The coefficient of friction for bike tires can vary depending on the surface and the condition of the tires. On average, it is around 0.7 for dry pavement and 0.4 for wet pavement. However, it is always best to consult the manufacturer's specifications for your specific tires.

3. Do the weight of the rider and bike affect the force of the tires with brakes?

Yes, the weight of the rider and bike will affect the force of the tires with brakes. The greater the weight, the greater the force needed to stop the bike, and vice versa. This is why it is important to regularly check and adjust your brakes to ensure they can handle the weight of the rider and bike.

4. How does the surface condition affect the force of the tires with brakes?

The surface condition can greatly affect the force of the tires with brakes. On a smooth and dry surface, there is less friction, so less force is needed to stop the bike. On a wet or uneven surface, there is more friction, so more force is needed to stop the bike.

5. What other factors can affect the force of bike tires with brakes?

Other factors that can affect the force of bike tires with brakes include the type and condition of the brakes, the speed of the bike, and the angle of the surface. It is important to regularly maintain and check these factors to ensure safe and effective braking while riding your bike.

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