Dynamics - Rock in tire tread *please check answer*

In summary, the conversation is about a problem involving a pebble on a rotating wheel. The person asking for help has provided a diagram and attempted a solution, but is unsure if it is correct. Another person points out a small error and explains the concept of normal forces. The first person realizes their mistake and the conversation ends with a clarification on the direction of the friction forces.
  • #1
bodaciousllam
2
0
I really have no idea if I even went about this problem right, maybe some of you wonderful people can help me out.

Homework Statement


http://img217.imageshack.us/img217/9358/wheeljk9.jpg

The Attempt at a Solution


http://img220.imageshack.us/img220/179/50999155cw8.th.jpg
 
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  • #2
Welcome to PF! Your solution looks good! Note that the friction force in your diagram,
2(F_f), acts radially inward on the pebble; but you also show a friction force in what you are calling the 'theta' direction (parallel to the rotation axis), which is zero, because there is no acceleration in that direction.
 
  • #3
Jay,

Thanks, but I can't figure out why the answer came out negative, unless it means I have the friction vectors pointing the wrong way, but that doesn't make sense to me intuitively.

And the theta friction force was just something I forgot to erase
 
  • #4
Oh, yeah, I missed your minus sign. The plus and minus sign difficulties are typical of all Physics problems. Actually, as your sketch shows. there are 2 Normal forces acting on the pebble; they act in opposite directions, each pointing toward the pebble, so that one value is negative (-323 N), and the other is positive (+323 N). The normal forces act toward the object they act on. It's probably better to just give the magnitude of the normal force, and show the direction in a sketch. Note that the friction forces on the pebble act radially inward, as they must in order to keep the pebble moving in the circle, in the inward direction of the centripetal acceleration. When the static friction force is not sufficient to produce the inward centripetal acceleration, that is, when the rpm exceeds 4000rpm, the pebble is flung off in a direction tangent to the circular path.
 

Related to Dynamics - Rock in tire tread *please check answer*

What is the purpose of studying dynamics in relation to rocks in tire tread?

The purpose of studying dynamics in relation to rocks in tire tread is to understand the behavior of rocks when they become embedded in the tread of a tire. This information can help improve tire design and safety, as well as provide insight into the mechanisms of rock movement.

What factors affect the dynamics of rocks in tire tread?

Several factors can affect the dynamics of rocks in tire tread, including the size and shape of the rock, the speed and direction of the vehicle, the type of tire tread, and the surface of the road. Additionally, the weight and distribution of the vehicle's load can also play a role.

How does the presence of rocks in tire tread affect vehicle performance?

The presence of rocks in tire tread can significantly impact vehicle performance. Rocks can cause vibrations, affect traction, and even puncture the tire, leading to loss of control or a flat tire. This is why it is important to understand the dynamics of rocks in tire tread and design tires that can effectively handle them.

What methods are used to study the dynamics of rocks in tire tread?

Scientists use a variety of methods to study the dynamics of rocks in tire tread, including laboratory experiments, computer simulations, and field studies. Each method has its advantages and limitations, and a combination of approaches is often used to gain a comprehensive understanding of the phenomenon.

Are there any real-world applications of studying dynamics in relation to rocks in tire tread?

Yes, there are several real-world applications of studying dynamics in relation to rocks in tire tread. This research can inform the design of tires for different types of vehicles and terrains, help improve road safety, and contribute to the development of more efficient and durable tires. Additionally, understanding the behavior of rocks in tire tread can also have implications for other fields such as geology and materials science.

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