The resistance a surface or object encounters when moving over another.
3
votes
4answers
554 views
Why would it be true that people with longer legs walk faster than ones with shorter legs?
When a person walks, the only force acting on him is the force of friction between him and the ground (neglecting air resistance and all). The magnitude of acceleration due to this force is ...
3
votes
1answer
425 views
Rope wrapped around a cylinder
If a rope is wrapped aound a cylinder what is the relationship between the amount of wrap and the ability to resist slipping off of the cylinder? An example would be if I had a 180 degree wrap and ...
3
votes
7answers
1k views
Simple friction formula for a car
I am making a 2D driving video game, and I would like to know the "simple" formula for calculating the friction force between the car and the road. I have read lots of friction diagrams involving ...
2
votes
5answers
388 views
How would you improve braking capability on a hovercraft?
Pretty much letting my mind free-wheel.
Assume a fleet of air-supported hover-craft were to replace cars/etc on the streets. Assume also that the present traffic-signals/pedestrian rules remain ...
2
votes
4answers
888 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 ...
2
votes
4answers
966 views
Why does soap make shaving with razor less painful?
The lubricant is needed only on the hair surface? How can the blade cut the slippery surface?
Why does soap make shaving with razor less painful?
2
votes
1answer
190 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 ...
2
votes
2answers
1k views
why making a surface “super” smooth increases the coefficient of friction?
I read that:
If you take a rough surface and make it smooth, the coefficient of friction decreases. But if you make it super smooth, then the coefficient of friction increases. How come?
2
votes
1answer
277 views
Static Friction in Free Body Diagram (FBD) of Car parked on Incline
I'm working on a sample problem and it asks on how steep of an incline can a car park? From what I learned the friction is in the opposite direction if there was motion in said friction-less ...
2
votes
1answer
76 views
How do I account for the direction of friction acting on a spring?
I would like to set up the equations of motion for a simple spring oscillator.
Let's have a spring lying horizontally; we attach a small mass $m$ to the (massless) spring.
The force of the spring ...
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 ...
2
votes
2answers
246 views
Does a ski racer with a larger mass have an advantage?
Does a ski racer with a greater mass have an advantage over a racer with a lesser mass?
If mass of one racer is 54 kg and the mass of a more slender racer is 44 kg I know the speed at which they ...
2
votes
1answer
3k views
Torque Required For a Motor to Move an Object on Wheels?
I've been attempting to calculate how much torque a motor needs to produce in order to start a stationary object on wheels moving. (The torque is being applied to the rear 2 wheels, the front 2 are on ...
2
votes
4answers
609 views
Why does a tire produce more traction when sliding slightly?
It is well known in racing that driving the car on the ideal "slip angle" of the tire where it is crabbing slightly from the pointed direction produces more cornering speed than a lower slip angle or ...
2
votes
1answer
113 views
Angular momentum conservation while internal frictional torque is present
So this appears in a problem which looks simple enough in its context; It's something like this:
Two discs, A and B, are mounted coaxially on a vertical axle. The discs have moments of inertia $I$ ...
2
votes
1answer
119 views
Two masses attached to a spring
I'm trying to understand the solution of the following problem.
Two masses $m_{1}$ and $m_{2}$ slide freely in a horizontal frictionless track and are connected by a spring whose force constant is ...
2
votes
1answer
115 views
Skiing downhill
The other day on skiing holiday we've been arguing about whether an adult has weight advantage over a child when skiing downhill.
I was claiming that gravity is a constant regardless of object's ...
2
votes
2answers
133 views
How can a train locomotive generate enough traction to pull all the coaches?
Sorry for posting what may be an obvious question but we just learning about friction at school and my teacher couldn't explain well enough to me and I would appreciate your inputs.
Consider the ...
2
votes
1answer
81 views
Which theory predicts that dubbed tires have more friction?
The physical reasoning I suppose could be that more contact areas mean more and higher friction. But is there an actual formula or a more mathematical explanation?
Application for bicycling was my ...
2
votes
2answers
354 views
Does kinetic friction increase as speed increases? [duplicate]
Possible Duplicate:
Does the force of kinetic friction increase with the relative speed of the objects involved? If not, why not?
Layman alert...I last did physics in high school, and am ...
2
votes
1answer
123 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 ...
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 ...
2
votes
2answers
247 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 ...
2
votes
3answers
959 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 ...
2
votes
3answers
138 views
Effect of surface treatment on fair dice
If I have a perfectly balanced and thus fair cubic die, then polish 3 adjacent faces (so that their coefficient of friction is effectively zero) and roughen the remaining faces (so that their ...
2
votes
1answer
209 views
Thermal energy generated due to loss in kinetic energy when observed from two different frames of reference
A body is moving with a velocity $v$ with respect to a frame of reference $S_1$.
It bumps into a very heavy object and comes to rest instantaneously, its kinetic energy
$$\frac{1}{2}mv^2$$
as ...
2
votes
2answers
828 views
Does a car use friction to move?
When a car's engine injects fuel into the cylinder chambers, the reaction creates a force that generates rotational momentum to the shaft and over the transmission, it translates that power to the ...
2
votes
1answer
441 views
Physics needed to build a top down billiards game [duplicate]
Possible Duplicate:
How are these balls reflected after they hit each other?
I was wondering what sort of physics equations would I need in order to build a top down billiards game? I tried ...
2
votes
1answer
534 views
Does ABS cause a force that resists turning a car into a corner?
ABS systems work by allowing a tire to continue to rotate rather than "locking-up" (stop turning) due to loss of traction with the road surface. A rotating tire can influence the direction of the ...
2
votes
1answer
295 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 ...
2
votes
1answer
265 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 ...
2
votes
2answers
482 views
Conservation of angular momentum in helicopter
I have a small RC-controlled toy helicopter with removable tail rotor.
Suppose I remove the tail rotor, hold the tail with my hand, start the rotor until it moves with constant angular velocity and ...
2
votes
1answer
902 views
Rolling resistance and static friction
I am a bit confused about the relation between rolling resistance and static friction.
I have often heard that it is the static friction that lets the wheel roll. Consider the following two cases:
...
2
votes
1answer
1k views
calculating thermal energy [exam prep]
I'm preparing for a grade 11 physics exam but having trouble with a question:
a 19.9kg mass slides in a straight 28.8m line
experiencing friction with a coefficient of 0.105, how much thermal energy ...
2
votes
0answers
92 views
Why did increasing the Ackermann geometry in my race car make it faster in corners?
Ackermann geometry is used to account for the different radius arcs that the front tires follow when the steering wheel is turned from center. It's often expressed as a percentage: e.g. 25% Ackermann, ...
2
votes
1answer
82 views
Approximating Rolling/Sliding in 2D Shape
I'm trying to find more information on how a 2D shape (could be defined by a function, such as ellipse, or by a polygon) will roll across a surface. The shape could be nearly circular or quite ...
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 ...
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
3answers
430 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 ...
1
vote
1answer
352 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 ...
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?
1
vote
3answers
1k views
Terminal Velocity
Let Suppose a bullet of 2 gram is falling with the speed of 200km/h.
Now how can we know the time after which it gains it terminal velocity.
Also when it gain its terminal velocity the force of ...
1
vote
1answer
350 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?
1
vote
1answer
119 views
Is energy “destroyed” when walking?
Conservation of energy states energy can't be destroyed, but isn't energy used up when walking in a straight line? If your not walking up a slope, kinetic energy isn't converted to gravitational ...
1
vote
2answers
973 views
What are all the equations we use to calculate how bounces work?
I mean, what is the object's final displacement, or the function that describes the object's height over time (see [1]) of an object thrown by a height $h$ with a speed of $\vec{v_0}$, a mass of $m$, ...
1
vote
1answer
61 views
Friction on a conveyor belt
I was surfing through an Olympiad paper and I was caught with this question.
A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating with $1\, \tfrac{m}{s^2}$ ...
1
vote
1answer
77 views
calculating work done by friction
I want to calculate the work done by friction if the length $L$ of uniform rope on the table slides off. There is friction between the cord and the table with coefficient of kinetic friction $\mu_k$.
...
1
vote
1answer
147 views
How would you use the Euler-Lagrange equation to predict the motion of projectiles with linear (Stokes) drag (but no wind)?
My first instinct would be to use the force
$$\vec{F} =- \alpha \vec{v}$$
and therefore
$$V(\vec{r}) = \alpha \int_C \vec{v}\cdot d\vec{s} = \alpha \int_C \vec{v}\cdot \vec{v} dt = \alpha \int_C ...
1
vote
1answer
1k views
Two problems with free body diagrams. Contradictions (solutions are provided)
This problem is similar, but also different question from my previous question. They are both unfortunately long.
Problem/Solution #1
!
!
Quick Concept Check
a) Could someone briefly explain to me ...
1
vote
2answers
296 views
Linear motion with and without Friction
Could we still use Newtonian mechanics in a frictionless world?
