The resistance a surface or object encounters when moving over another.
3
votes
2answers
233 views
Will two trains running along the equator in opposite direction experience same wear out?
Two identical trains, at the equator start travelling round the world in opposite directions. They start together, run at the same speed and are on different tracks. Which train will wear out its ...
1
vote
0answers
23 views
Rolling (without slipping) ball on a moving surface 2 [duplicate]
Possible Duplicate:
Rolling (without slipping) ball on a moving surface
Apparently I didn't log in properly when I asked a question this morning: Rolling (without slipping) ball on a moving ...
2
votes
1answer
296 views
Rolling (without slipping) ball on a moving surface
I've been looking at examples of a ball rolling without slipping down an inclined surface. What happens if the incline angle changes as the ball is rolling?
More precisely I've been trying to find ...
1
vote
0answers
475 views
Newton's second-law word problems with coefficient friction [closed]
Here is an example problem:
A sled of mass 50kg is pulled along a snow-covered, flat ground. The static coefficient of friction is 0.30, and the kinetic coefficient friction is 0.100. What force ...
25
votes
6answers
1k views
Can I survive a free fall using a ramp and a rope?
Can I survive a free fall by carrying a very light and resistant ramp using a rope?
Note: lets assume the ramp is a little bit heavier at the bottom and I am very skilled at making it always land ...
1
vote
0answers
79 views
What is the angle of the string with the vertical?
A heavy uniform sphere of radius $a$ has a light inextensible string
attached to a point on its surface. The other end of the string is
fixed to a point on a rough vertical wall. The sphere ...
0
votes
2answers
92 views
Energy problem: What's wrong here?
A car ($m=540\,\text{kg}$) engine, has a power of $60\,\text{kW}$. The static friction coefficient between wheels and road is $k=0.6$. How long does it take to reach the speed of ...
0
votes
2answers
195 views
What is the force of friction between two bodies given their masses and a force pulling them as a unit accross a surface?
Where a force of 200N pulls two blocks together(as one system) across a horizontal table top(µ=0.800)
$m_A$ = 5.00kg, $m_B$ = 10.0kg
Find the acceleration of the system.
Find f$_k$ between B and A
...
2
votes
1answer
267 views
How does the resistance force on a rolling ball depend on the ball radius?
A billiard ball set gently rolling on a billiard table slows and stops, because it is decelerated by resistance forces at the contact between the ball and table.
I expect the magnitude of the ...
5
votes
2answers
152 views
Boy and box on ice
I have a troubles. Can you help me?
I have a task, called "slippery activity".
Boy (he has $m=45kg$) Stands at ice and tries to move a big box ($M=90kg$) with a string (rope). Boy's Slip ratio is ...
4
votes
2answers
502 views
How does rubbing cause the transfer of electrons from one object to the other? [duplicate]
I have just learnt about electrostatics. Why would there be a transfer of electrons? Is it because of the difference of the materials (i.e. triboelectric series)? So in the case of two different ...
5
votes
4answers
1k views
After what speed air friction starts to heat up an object?
I understand that air friction cools off an object at low speeds. For example, if you blow on a spoon of hot soup, it cools off. Or if you swing a hot frying pan in the air, it cools off faster.
But ...
2
votes
1answer
125 views
Understanding Work and the conservation of energy
We have a car with a mass of $780 kg$ with travels with a speed of $50 km/h$. The car brakes and after $4,2m$ is stops completely. Warmth is created. Calculate the friction.
I solved this easily, by ...
1
vote
3answers
354 views
Conservation of energy in objects at terminal velocities
In vacuum, object free falling under gravity, the sum of Gravitational Potential Energy(GPE) and Kinetic Energy (KE) is a constant. The GPE is a decreasing side of a quadratic and KE is a increasing ...
2
votes
1answer
100 views
Moving along friction surfaces
If a particle moves along a one dimensional surface with constant friction. As the particle moves from point $A$ to point $B$ it loses an amount of energy equals $E(A,B)$. Consider that the particle ...
22
votes
5answers
4k views
Why does a tire need to be filled with air?
The Mini 4WD's tires aren't full of air, and it can run. Also, the tank doesn't have tires with air. So, the question is: why do real cars on the road need to be filled with air? What is the idea ...
0
votes
0answers
38 views
Why do bigger tires = more friction? [duplicate]
Possible Duplicate:
Why do people recommend wider tyres in car for better road grip?
Static/kinetic friction says that the friction force is proportional to the normal force, via the ...
0
votes
0answers
74 views
Describing the movement of the object in a particular situation in Lagrangian way
Suppose there is a object M, (sliding motion) moving by the initial speed $v$ and the initial location $x_0$. Otherwise noted, friction is assumed to be nonexistent. It then meets a circular mold ...
0
votes
1answer
441 views
Is water considered a substance with low friction or high friction?
Like, for example, rubber is a substance with high friction, as an object with neither high or low friction would easily stop on it, and wouldn't skid. Ice is considered an object with low friction, ...
3
votes
2answers
185 views
Does air resistance ever slow a particle down to zero velocity?
If a particle moves in a place with air resistance (but no other forces), will it ever reach a zero velocity in finite time? The air resistance is proportional to some power of velocity - $v^\alpha$, ...
2
votes
1answer
84 views
Beer bottle leftovers pour quickly only after waiting?
Why is it that after pouring a delicious beer from a bottle, I can hold it upside down for several seconds without reward, but if I wait a bit, the remainder presumably settles at the bottom and ...
0
votes
0answers
21 views
Helpful tutorials on force [duplicate]
Possible Duplicate:
List of good classical physics books
I'm having a hard time understanding force in my highschool AP physics class, i looked through youtube but without luck. Could ...
1
vote
3answers
434 views
Is it possible to find out the distance traveled by a car if the force applied on it is given?
Say you have car which produces $F$ amount of force which is transferred to the wheels directly.
Now assuming that there is air friction which is causing a retarding force proportional to the ...
2
votes
4answers
904 views
Physics behind Wheel Slipping
Lets say that I'm in a car and I apply full acceleration suddenly. Now, the wheels would slip and hence the car doesn't displace much.
But If I start with some constant acceleration, slipping doesn't ...
1
vote
1answer
278 views
Overcoming Friction
Let's say a box is moved by attaching a rope to it and pulling with an applied force at a certain angle. Now, let's say that this is being done on an inclined ramp. How would I find the acceleration?
...
14
votes
3answers
603 views
Why doesn't a fly fall off the wall?
Pretty simple question, but not an obvious answer at least not to me. I mean you can't just place a dead fly on the wall and expect it to stay there, he will fall off due to gravity. At first I ...
3
votes
1answer
555 views
Where does the lost energy go in a rubber band powering a rotating shaft?
Okay, I'm no physics whiz, and this has me stumped. You know those toy airplanes you can get with the rubber-band driven propellers? You twist the propeller a bunch of times, and this stores ...
1
vote
1answer
129 views
Friction between atoms in spring
if i doing experiment on spring-mass system in vaccum,if i pull the to some extent (within elastic limit of spring) & let it go,will the system oscillate indefinitely? (neglect contact frictions ...
1
vote
1answer
233 views
Kinematics - Find theta with Coefficient of Friction?
I recently found a problem that looked like this:
A box sits on a horizontal wooden ramp. The coefficient of static friction between the box and the ramp is ...
2
votes
2answers
248 views
Force applied perpendicular to direction of motion, static or kinetic friction?
Let's assume we have a 1 kg cube on a flat uniform surface. The coefficients of friction between them are $\mu_k = 0.25$ and $\mu_s = 0.50$. This cube is moving at 1 m/s in the y direction, with ...
1
vote
1answer
355 views
Direction of friction on particle placed on a rotating turntable
If a particle is placed on a rotating turntable then the particle has a tendency to slip tangentially with respect to the underneath surface... So the friction should act tangentially to the ...
0
votes
1answer
129 views
Friction in Physics
I've heard a lot of things about Friction like friction between solids, liquids and gases. Even practical applications like motion of objects (Like car moving on road), etc. involve friction. But, do ...
0
votes
2answers
774 views
Physics behind Water drops during falling from a tap
what is physics behind Water drops during falling from a tap.
water drop animation
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces.
Why Water ...
0
votes
1answer
2k views
How to calculate work done by variable kinetic friction force?
A heavy chain with a mass per unit length $\rho$ is pulled by the constant force $F$ along a horizontal surface consisting of a smooth section and a rough section. The chain is initially at rest on ...
3
votes
1answer
295 views
Change in appearance of liquid drop due to gravity
A liquid drop is spherical in shape due to surface tension. But why does it appear as a vertical line under the free-fall due to gravity? (E.g. During a rain - falling raindrop) Is there a specified ...
2
votes
3answers
960 views
How do I find work done by friction over a curve represented by a polynomial?
I am facing a problem in Physics.
Problem: What will be the work done by the frictional force over a polynomial curve if a body is sliding on this polynomial($a+bx+cx^2+dx^3+\ldots$) curve from rest ...
0
votes
0answers
542 views
Capstan equation [closed]
This problem is from An Introduction To Mechanics book, chapter 2, problem #24.
A device called a capstan is used aboard ships in order to control
a rope which is under great tension. The rope is ...
0
votes
0answers
67 views
How to control heavy ball in x and y direction? [closed]
I'm trying to build a device that holds a rather heavy ball and I want to be able to control it's "movement" in the X and Y directions (they are horizontal as well as orthogonal).
My current ...
1
vote
1answer
164 views
What controls whether a ball will skid or roll?
A billard ball is struck with a cue. The line of action of the applied impulse is horizontal and passes through the center of the ball. The initial velocity $v_0$ of the ball, its radius $R$, its mass ...
0
votes
2answers
119 views
What is the origin of nonconservative force?
My understanding about conservative force is a force that its work is independent of path such that we can construct another form of the work called potential to make our life easier.
For friction, ...
0
votes
1answer
197 views
Is my understanding of the mechanics of skidding correct?
I'm trying to understand the mechanics which determine if a car making a turn will skid.
Are the following correct or incorrect:
A vehicle making a turn will skid unless the centripetal force is ...
4
votes
4answers
191 views
Friction at zero temperature?
By the fluctuation-dissipation theorem (detailed-balance for Langevin equation), $$\sigma^2 = 2 \gamma k_B T$$ where $\sigma$ is the variance of noise, $\gamma$ is a friction coefficient, $k_B$ is ...
0
votes
0answers
107 views
A problem on mechanical energy and friction
I'm studying for a mid-term, and I'm trying to solve some mock-papers. The following are two problems which I have solved, but I'm missing a part:
$(1)$ A body of mass $ m_1= 8 \rm kg$ passes ...
2
votes
1answer
192 views
When does centripetal force cause constant circular motion?
As far as I know, if an object has a speed $s$ and a force is applied to it which generates an acceleration of $s^2/r$, then the object will start moving in a circle of radius $r$. Also, as far as I ...
1
vote
1answer
101 views
What prevents a natural fibers rope from untwisting when it is elongated?
I don't understand why a rope doesn't untwist when an attempt is made to increase its length. It seems counter-intuitive to me, because untwisting would allow the rope to increase its length, but in ...
1
vote
1answer
353 views
What would it feel like to touch a frictionless surface
Assume there is a completely frictionless surface. Would touching such a surface be possible? If so, what would it feel to the touch?
5
votes
1answer
2k views
Why do people recommend wider tyres in car for better road grip?
Tyre companies boast of their wider tires for better grip on road. Also, the F1 cars have broad tires for better grip. But as far as I know Friction does not depend on the surface area of contact ...
3
votes
3answers
853 views
Does friction decrease as objects move faster against each other?
I was told that the faster two objects move against each other, the less the friction between them would be… compared to if they were moving slower. In physics class, we always use the coefficient of ...
1
vote
1answer
295 views
What forces act on a person sitting in a chair with wheels when they push off another stationary object
What is slowing me down when I push off my desk?
What are the "Major" contributors? and
Does how hard I push with one hand (or with two hands) make a
significant difference?
3
votes
1answer
163 views
What is the function of the top point of a bouncing ball?
A ball is thrown away as parallel to x axis from M(0,h) point with speed V . After each jumping on x axis , it can reach half of previous height as shown in the figure.(Assume that no any air ...
