# Questions tagged [friction]

The resistance a surface or object encounters when moving over another.

209 questions with no upvoted or accepted answers
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### Why does no slipping occur when a particle is attached to a string, which is wound onto a circular disk, and the system is allowed to move?

In this question, the only way we can find the angular acceleration of the disc is by equating it to the linear acceleration of the particle divided by the radius. But this holds only if the string ...
1k views

### Is coefficient of friction is always less than unity?

Is the coefficient of friction always less than unity? What are the cases in which coefficient of friction is greater than unity?
627 views

### Is it possible that water flow stops in a very long pipe due to friction forces?

I've been thinking about a hypothetical problem concerning fluid flow across two distant countries. Assume that country A wants to share water from a river with country B. Country A builds a dam to ...
780 views

### Massive pulley, torque and tension

Given a pulley and two masses, like so: Take the pulley to have a non negligible mass, zero friction between pulley and axle, but enough friction between pulley and rope such that the rope doesn't ...
85 views

### Intuitive Understanding of Mass, Acceleration, Friction Force and Coefficient of Friction?

When calculating maximum acceleration, I know that mass cancels out to get: $$\mu_s = a/g$$ Is there an intuitive approach to this? Here's a problem that involves this: If half of the weight of a ...
114 views

### Kindling to make a fire

I know that rubbing stuff like dry grass or wood on firewood works to make a fire but why does it work? I think it is because the friction produces heat but then how come our hands don't get on fire ...
68 views

### treadmill physics, wheel size vs. counterforce

I'm trying to design a classical treadmill for rodents which has two wheels at the two end and a plain "conveyor" belt in between. What is the best way of designing this if i want to have minimal ...