# Tagged Questions

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

6k views

### Why are a motorcycle's front brakes more effective than back?

I've noticed that when I apply the front brakes on my bike it stops quite quickly. If I apply the back brakes at the same speed, it skids rather than stopping quickly. Why?
255 views

### Confusions in the 'Adhesion Theory of friction.'

While reading about the Adhesion theory of friction on this site, I came to some points which I couldn't understand. I have highlighted them: ...Adhesion approach is based on the partial ...
397 views

### A question about a body moving in horizontal circular motion

I have some related questions about a body moving in uniform horizontal circular motion: The body moves with a constant angular velocity on a rough horizontal surface. It is attached to a string that ...
2k views

### 6 wheels more efficient than 4 wheels?

Which would be easier to push in a straight line, a flat cart with 4 wheels or the same cart (and same load) with the same size wheels, but has six wheels? and why? Thanks
11k views

### How fast would someone have to run to travel vertically up a wall?

I am currently doing a physics project on the effects of so-called 'super-speed'. I was wondering how fast you would have to run to vertically travel up a wall? That is, to negate the force of gravity....
344 views

### How to model a very simple spinning wheel

First off, I'm not a physics person, just a lowly software engineer with below average math skills. What I've written is a simple animation of a spinning wheel using C++/GTK/Cairo. It allows the user ...
135 views

### Space elevator: a Earth rotation brake model

I read this article regarding the space elevator. A very long carbon nanotubes string, running from the Earth surface into the vacuum of the space. Tension and friction, an enormous quantity of ...
504 views

### Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling. While I was doing this, I encountered many curves like those shown below. While I understand the need of slip angles to ...
992 views

### What could be the applications of Damped Oscillation? [closed]

I've been researching on Damped Oscillation for a few days for a research paper, however I couldn't find any of its applications on the web, though there are few examples of it, but they couldn't be ...
621 views

### Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
5k views

### Why does friction play the role of centripetal force during the turning of a car?

What makes frictional force the centripetal force of a car turning along a curve? As friction is the opposing force and acts anti-parallel so there is no component of frictional force towards the ...
13k views

### If mass is added to a toy car does it affect its speed making it faster

If mass is added to a toy car (29.7g) and dropped down a wooden ramp would it affect its speed making it go faster? I know friction comes in to play to, so if you could give me an answer or an ...
176 views

### Twisting a tightly fitting rod

Consider the task of extracting a cylindrical rod held by friction in a tightly fitting shaft. Instinctively one would tend to twist the rod around its axis while pulling. The question is, what is ...
3k views

### Effect of steering a car at high speed

I take it the angle of the steering wheel in a car is roughly proportional to the curvature, and therefore inversely proportional to the turning radius. When I am driving slowly and want to turn the ...
170 views

### What is the physical interpretation of the linear coefficient in this ODE for projectile motion?

For the second order ODE governing the position of a projectile subject to air resistance $$m\frac{d^2x}{dt^2} +k\frac{dx}{dt}+mg=0 \quad k>0, \> x(0)=0, \> x'(0)=V>0$$ a non-...
2k views

### How can we minimize the coefficient of static/kinetic friction?

Static frictional force depends on the coefficient of static friction; kinetic frictional force depends on the coefficient of kinetic friction. To minimize friction, one of two things could happen: ...
40 views

### How to calculate heat generated from cosmic dust in space? [duplicate]

Say I have a spaceship, and I'm flying it through space at a constant high velocity V. The spaceship is pretty large (big surface area). In space however, there is cosmic dust scattered throughout (...
198 views

### Distinction between torque and force

Distinction between Torque and Force. Consider a case when a cylinder is rolling down a rough inclined plane. While analysing its motion, we consider the force applied by the friction and the ...
41 views

### Everyday Low-Energy Atom Collider

During the shearing of metal in a machining process, what exactly is the source of the heat that is produced? I realize that the energy is coming from the work being done by the cutting tool. I am ...
487 views

### Accelerated wedge [closed]

Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative. The coefficient of friction between the mass and the wedge ...
939 views

### Direction of friction force between two boxes

There are two boxes on top of each other. The bottom box is dragged right by a constant force. What is the direction of friction of the top box against the bottom box?
743 views

### Nails and Screws without Friction

In my physics class we're just starting the chapter on friction, and our book began the chapter by describing what a world without friction would be like. Among other examples, it said "nails and ...
5k views

### Why do computers generate heat?

Computers generate heat when they work. Is it a result of information processing or friction (resistance)? Are these just different ways to describe the same thing? Or does some definite part of the ...
131 views

### The forces acting on 2 boxes [closed]

Consider the following figure: The surface is not friction-less. When the force $F$ is applied on mass A: Is the force the mass A applies on mass B larger, smaller or equal then the Force that B ...
651 views

### How torque and friction cause wheel to roll

I apologize if this question has been answered before, but I did not find the explanation that I needed. If a torque is applied to a wheel situated on a frictional surface, what forces cause the ...
34 views

### Why does a cyclist/motorcyclist bend when making a turn? [duplicate]

I've seen this very prominently in the Olympics
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### Static and kinetic friction [closed]

Say you have block1 on top of block 2 and the whole system is accelerating toward the right at a certain acceleration. Due to inertia block 1 wants to move backward to the left so there has to be a ...
7k views

### Pulling apart two interleaved phone books

The TV show Mythbusters had an episode in which they interleaved two phone books and dramatized how hard it was to pull them apart. (A long time ago, a phone book was a book that had an index of phone ...
4k views

### Calculate coefficient of friction from deceleration with and without conservation of energy

How can I solve the following problem? A block that moves at the speed of 120 cm / s keep going for 70 cm before stopping. What's the coefficient of friction between block and table calculated ...
130 views

### Could $\int (\ddot\phi + \mu\dot\phi^2)d\phi$ ever be negative? How to show it?

I am working on the following problem: Given a mass $m$ at rest at the base of an incline surface shaped like 1/12th of a circle with radius $R$. The mass is pulled up the incline by a rope that ...
386 views

### How many molecules rub off when I press a key?

I have a lot of questions below but my overarching questions are: Do surfaces rubbing lightly together always strip molecules off of each other? and How can we model that? Clearly the answer to the ...
33 views

### Why do skidding wheels have less traction than non skidding wheels? [duplicate]

I do not understand in terms of coefficients of friction why this happens? From my understanding the ground and the tire still have the same coefficients of friction right? So why is there less ...
6k views

### Why does the co-efficent of kinetic friction of a block on an inclined plane not change when you increase the angle of the plane?

The coefficient of kinetic friction can be calculated using $\mu_k = F_k/F_n$. A change in angle does not affect the normal force, but doesn't a change in angle affect the friction? As in if the angle ...
185 views

### Pseudoforce and friction: confusion

Consider the following situation. A block of mass $M$ is resting on a rough horizontal ground, and a frame is moving towards the right horizontally with an acceleration $a$. Suppose the coefficient of ...
1k views

### Who does work while walking?

While walking the work done by friction is zero. But who does the work, actually? How someone is getting displaced? This situation also arises when someone climbs without slipping or is climbing a ...
630 views

### Why is there a static frictional force on an object that rolls without slipping?

It is clear that if a frictional force must exist on an object that rolls without slipping, it must a static frictional force because the contact point of the object with the ground does not move. I ...
52 views

### A statics problem to find minimal friction

consider the following: I need to find the minimal coeeficient of friction $\mu _{min}$ so that both recatngle boxes would remain static. The lower angle in the triangle is $2\alpha$ as indicated. I ...
4k views

### How does static friction increase with increase in the applied force?

My book says that 'Between surface of contact between two bodies there are contact forces applied between each other (they are equal in magnitude but opposite in direction,obeying Newton's 3rd law) ...
322 views

### Finding coefficient of friction between block and plane [closed]

An inclined plane makes angle $\theta$ with horizontal. Upper half plane is perfectly smooth where as lower half is rough. The block of mass m starts sliding from top. If the block again comes to rest ...