1
vote
1answer
41 views

What force counteracts friction when a block is pulled?

Firstly, I understand and apologize that this is more of a physics question than a math question. I noticed that when I pulled a book out from under a pack of gum, the gum stayed largely in place (it ...
7
votes
3answers
921 views

What determines whether a pool ball will bouce backwards after colliding with another pool ball?

I'm no knowledgeable pool player, but I've noticed that sometimes when the cue ball hits another pool ball, they roll together; and sometimes the cue ball bounces back. And I have a very, very rough ...
0
votes
1answer
54 views

How to calculate energy to start movement?

So let me try to explain a little bit. Lets say I have a robot on wheels. I want this robot to push a block. Lets say the force to produce in order to move that block is 100N. How much energy will I ...
0
votes
1answer
29 views

Kinematics - moving body [duplicate]

If I have an inclined plane, which has acceleration $\alpha$, will a block placed on the inclined plane slip back with the same acceleration? (considering that the surface is frictionless)
0
votes
1answer
41 views

Does a Force on the block $M_1$ in this diagram have an effect on the block $M_2$?

Suppose we have two blocks: There is no friction. Does $F$ has the same effect on $M_2$?
0
votes
2answers
60 views

Why is the force of Friction less than the force applied on the block in this situation?

This is a seemingly basic mechanics problem but I'm having a dilemma in understanding what happens. You start with two blocks, one on top of the other (the bottom block has a larger mass than the top ...
2
votes
1answer
31 views

How does separation of tracks affect the acceleration of a rolling ball on the tracks?

If I have two metal rods arranged like a ramp with coefficient of friction $\mu$, at an angle $\theta$ to the ground, and a solid metal ball or radius $r$ and mass $m$ rolling down between the two ...
35
votes
7answers
5k views

How can the Earth keep spinning with a liquid core?

In regards to the 'conservation of angular momentum' being the explanation of why celestial objects spin... If you fill a ball or any other container with a liquid and try to spin it, you will not ...
0
votes
1answer
58 views

Force on a potentially rolling ball initially at rest

I'm a graduate student in mechatronics, but I give myself headaches on this astonishingly simple 2D problem. Imagine a ball (perfectly rigid) on an horizontal plane (perfectly rigid), initially at ...
1
vote
1answer
30 views

How to identify whether the friction is kinetic or static?

The body 'A' is moving forward with certain acceleration over the ground. The ground applies a kinetic friction force on 'A' in backward direction to oppose the relative motion. The block 'A' also ...
1
vote
1answer
42 views

Throwing ball against oily/slippery wall

I would like to know whether a ball bounces back normally if you throw it against an oily wall. Like a wall watered down with oil. Basically I want to know if it will actually slip before bouncing ...
1
vote
1answer
49 views

Block and Pulley Problem with Friction [closed]

1.) What is the acceleration of the hanging mass? (Indicate the direction with the sign of your answer.) 2.) Determine the tension in the cord. (Indicate the direction with the sign of your ...
1
vote
0answers
41 views

Friction force problem for a 4 wheel drive Car [closed]

The car is a 4 wheel drive in equilibrium, the car doesn't touch the ground with the front wheel (A) but is in contact in B with the sidewalk (the sidewalk has a hight equal to $h$), the friction ...
1
vote
3answers
94 views

Why doesn't a block rotate due to friction?

In a horizontal surface, a block (cube) is sliding due to a sudden push. When the block slides, there is frictional force which is acting on the block. Frictional force will have a torque around ...
2
votes
3answers
139 views

Is friction a product of Newton's third law?

Newton's third law is defined as $F_{12} = -F_{21}$ Is friction a product of this law? For example, if I take my hand and slide it across the floor in the $+x$ direction... My hand exerts a force ...
1
vote
3answers
228 views

Why is using Newton's First Law failing me?

A factory worker pushes a 29.7kg crate a distance of 5.0m along a level floor at constant velocity by pushing downward at an angle of 32$^\circ$ below the horizontal. The coefficient of kinetic ...
5
votes
1answer
77 views

How can a reel of thread move in opposite direction?

There is a nice puzzle about reel of thread. I wonder why the solution works. The puzzle: You take a reel with threads on it. Inner radius r, outer radius R. You put it on a table. If you pull ...
0
votes
2answers
81 views

Is friction always constant?

Can the norm of the friction force change with time? Notice I said the norm which is in Newtons, can it change with time? Sorry if the question seems a bit confusing but I've done my best to explain. ...
1
vote
1answer
30 views

Clarification what exactly this question wants regarding force [closed]

I would like to ask you if the question asked What is the minimum force parallel to the plane, which can be prevent the block from slipping down the plane? I just did the calculation and and ...
2
votes
2answers
107 views

kinetic and potential energy

I have 2 cubes where one mass is greater than the other. $M$ and $m$, where $M>m$, and there is a hill that is symmetrical on both sides, and has a friction factor of $k$ between the object and the ...
0
votes
1answer
38 views

graphing velocity and time (v-t graph) [closed]

The question goes like this: If we push a body shortly uphill and it gets a starting velocity of $v \ ms^{-1}$,the coefficient of friction between the body and the surface is constant, represented by ...
3
votes
3answers
93 views

Time reversal symmetry in the presence of friction

I was reading a paper on time reversal symmetry, and came across an example of a pendulum swinging in the presence of friction: When we consider the more realistic physical situation of a swinging ...
0
votes
2answers
57 views

Physical interpretation of initial conditions for damped mass-spring system

I have background in pure mathematics so my question is about physical meaning. If we consider equation for damped mass-spring system, it is linear ordinary second order differential equation. So to ...
1
vote
2answers
90 views

Why neglect friction when computing torque?

There is a block of wood on a plank, with friction, and the block is moving down with uniform speed. They are asking what is the torque acting through the center of the block. My doubt is that ...
0
votes
0answers
54 views

Calculating the rate at which a car turns

This is going to be difficult to describe, as I have no real concept of this sort of physics, so please bear with me. If this is too much or beyond the scope of this website, I apologize. I am making ...
1
vote
0answers
42 views

Uniform Circular Motion with Banked Road and Car [closed]

In Uniform Circular Motion, if a car is rounding a curve at a certain speed, and the angle of the road allows the car to drive around at that speed, that speed is called the "design speed." If the ...
1
vote
1answer
146 views

Mechanics question - ladder leaning against a wall

I am struggling with part a) of this question: Here is the solution: In part a) they prove that $F \leq \mu R$ is false for this system. So as $F$ is neither less than nor equal to $\mu R$ it ...
3
votes
2answers
85 views

Consider a horizontal surface with or without friction. Ideally, will a wheel rolling without slipping roll forever in both cases?

Suppose a wheel is rolling smoothly on a horizontal plane i.e., it is rolling without slipping. Now let's take the two cases of the horizontal plane: It has friction It is frictionless In the ...
1
vote
0answers
45 views

What determines the speed required to pull a table cloth?

I was watching this show "Street Genius" on National Geographic and the host Tim Shaw demonstrated an experiment about Inertia, What he did was, He tied one end of a table cloth to a car through a ...
0
votes
1answer
46 views

Static friction

Just a quick question, When a force on an object is equal to its static coefficient * normal force , would the object move or would it stay stationary? Or does the force always need to be greater ...
3
votes
0answers
36 views

How much weight is lifted from each side? [closed]

I don't know the math to do this, so I am asking here if someone can work this out with all of the details I'm providing. Total mass EST.: 2,400 lbs. Length from front to back: 14 feet 6 inches. ...
1
vote
1answer
56 views

High-School Physics with inclines [closed]

The figure below shows two blocks with a rope that runs over a pulley. The mass of $m_2$ is 5.0 kg and the incline is 35 degrees. The coefficient of static friction between $m_1$ and the inclined ...
0
votes
1answer
87 views

Finding friction forces of stacked boxes on a table

Consider the following system. The given friction coefficients are for static. Let $g=10$ (meter per square second). If the $F(t)=10t$, for example, determine the friction forces $f_{AB}(t)$ ...
2
votes
1answer
138 views

How is circular motion possible on a banked road when there is no Friction?

It is given here that the maximum safe speed of a vehicle on a banked road having coefficient of friction $0$, is $V =\sqrt{R g \tan \theta}$, where $\theta$ is the angle of banking. I can't ...
1
vote
2answers
58 views

Centrifugal force when there is no friction [duplicate]

Assume that a coin is placed on circular disk and now a disk is rotated with constant angular velocity. If there is no friction between the surfaces of a disk and coin, according to theory the coin ...
1
vote
1answer
90 views

Calculating the time to stop a wheel with friction [closed]

I'm trying to solve the following problem, but i have no idea how to begin. A wheel of mass $M$, radius of gyration $k$, spins smoothly on a fixed horizontal axle of radius a which passes through ...
1
vote
3answers
308 views

How long does it take for an electric car to go from 0 to 60 mph?

I found the freefall motion equation which describes terminal velocity of a falling body, but I can't find a similar equation for a vehicle subject to constant traction force, so I tried determining ...
0
votes
3answers
84 views

Newton's third law of motion

Action has equal but opposite reaction then, why dont a ball keep on moving when made to move between two surfaces,should elasticity of surface,gravity and friction be mentioned in this theory?
4
votes
4answers
731 views

Blocks stacked on an incline connected by rope around pulley

Two objects A and B, of masses 5 kg and 20 kg respectively, are connected by a massless string passing over a frictionless pulley at the top of an inclined plane, as shown in the figure. The ...
1
vote
0answers
62 views

Block on block with friction [closed]

I couldn't find a similar question here - I'm guessing because it's kind of elementary. Lets say we have two blocks, $B_1$ and $B_2$, of mass $m_1$ and $m_2$ (respectively), where $B_1$ is directly ...
1
vote
2answers
299 views

Determining the direction of friction

I had a question which has always been of slight confusion to me. Say you are dealing with your typical block-on-an-angled-plane setup. You have a block with mass m that is initially at rest. The ...
2
votes
1answer
117 views

Accelerate the car by static friction

I asked this question about friction and slip ratio and now I still don't understand it Why friction is zero when wheel slip is zero? As the below graph of wheel friction vs slip ratio shows that in ...
9
votes
1answer
167 views

What makes a wrist-energized gyroscope rotate faster?

I'm considering a wrist-energized gyroscope, shown below (after my daughter let it fall and it broke open). That one was sold as Roller Ball, but variants are known as Powerball, DynaBee, Dynaball, ...
5
votes
1answer
76 views

Why is it easier to glide on sharp ice skates than on dull skates?

There have been previous questions (e.g. here and here) on Physics.SE about the mechanism that makes ice skating possible. Reviewing these, as well external references, it seems pretty clear that the ...
1
vote
2answers
111 views

Direction of friction for object that rolls with slipping

Let's say you hit a cue ball with a pool stick that causes an impulse. If the pool stick hits the ball above the ball's center of mass, is the direction of friction different than if the pool stick ...
0
votes
2answers
244 views

Rolling disk in inclined plane and flat plane? [duplicate]

A disk is rolling (not sliding) in the inclined plane with initial velocity of zero. So there is friction between disk and plane. But when we use the energy conservation rule, we consider as: ...
1
vote
2answers
288 views

Friction as a Centripetal Force

When an object is moving in a circle, won't the frictional force oppose it's motion? And if the velocity is always tangential to the path, there is no component of it towards the center, so there is ...
1
vote
2answers
89 views

Energy of a damped oscillator

$$ E=\frac{1}{2}m\left(\frac{dx}{dt}\right)^2+\frac{1}{2}m\omega_0^2x^2. $$ This is the equation for the energy of a oscillator. The second term is the potential energy. Now, my question is, will ...
2
votes
0answers
53 views

Can I use the reduced mass principle in a spring-damper system?

http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html#rm I want to know, if I can use the reduced mass principle to solve a two object spring-damper system. In the books and webpages that I have ...
0
votes
0answers
205 views

Damping ratio and damping coefficient of two objects connected by spring

There are two objects m1 and m2 connected by a spring and a viscous damper (e.g car body and wheel connected by spring) From wiki: $\zeta ={c \over 2{\sqrt {mk}}}$ ΞΆ is damping ratio, c is damping ...