1
vote
1answer
40 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 ...
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
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
0answers
22 views

Maximum rail adhesion utlilization during vehicle towing

Ok Physics Stackexchange, I've got a question for you regarding maximum adhesion utilization regarding railway vehicles (a EMU, with distributed motorized axles to be more specific) during a special, ...
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 ...
2
votes
3answers
138 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 ...
0
votes
3answers
49 views

Solving for Normal Force

I'm working through The Nature of Code, which is an awesome book, lots of fun. I've come across Exercise 3.13 and I'm not sure how to solve it. I'm assuming that the force of gravity and the force of ...
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 ...
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 ...
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. ...
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 $f_{AB}(t)$ ...
4
votes
4answers
725 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 ...
0
votes
0answers
75 views

Why friction force is force of constraint?

My understanding about constraint force is that it is a force which limits the geometry of particle's motion. For example, situations such as the particle trapped in a track or limited in domain can ...
0
votes
1answer
159 views

Help understanding a potential energy problem [closed]

Apologies if the following problem does not seem to involve potential energy, it is a homework problem that is labeled under the potential energy chapter. Question While a roofer is working on a ...
1
vote
1answer
1k views

Calculate work done in an inclined plane [closed]

How can you calculate the work done by a force (of unknown quantity) exerted on a 10kg block on an inclined plane. The force is pointing upwards and parallel to the incline (which is inclined 30 ...
-3
votes
1answer
65 views

Forces: why are the theta's equal?

I found this figure in my physics book, the task says that the incline got a angle of theta. How do figure out that the gravity and the y-axis got the same angle as the incline? There is no ...
-5
votes
1answer
394 views

Is it possible to find the coefficient of friction without frictional force? [closed]

I am working on the following problem: The braking acceleration for a car based on data in a driver’s handbook is –12.2 m/s2. If the car has a mass of 925 kg, find the frictional force and state the ...
-1
votes
1answer
66 views

What is the frictional force of this car? [closed]

The breaking acceleration for a car is $-12.2\frac{m}{s^2}$. The car has a mass of 925kg. I want to find the frictional force. Here is what I have so far: $$\Sigma\vec{F} = m\vec{a}$$ $$\Sigma\vec{F} ...
0
votes
2answers
754 views

What is the direction of static friction?

Note: My question is duplicate of the following Direction of friction when a car turns Why does friction cause a car to turn? I've gone through many related questions especially the first. As ...
-1
votes
1answer
93 views

What stops the car?

Centre of mass of a system cannot change its state of motion, unless there is an external force acting on it. Yet the internal force of brakes can bring a car to rest. Then what stops the car?
-1
votes
2answers
110 views

Friction acting on mass on string

Assume we have some stationary point mass that would slide, if not for some coefficient of friction, along a light, inextensible string, attached to two points at different heights. Considering ...
3
votes
1answer
148 views

If friction disregard area, why the direction you drag a long object matters?

I am talking here about dry friction between solid objects, for example a ruler and a table, not anything lubricated or fluid. I noticed that with a ruler and a table for example, if you drag the ...
0
votes
1answer
58 views

Find the force used to press a book against a leaned desk so it doesn't slip

I know there are several threads concerning this issue, but none of it helped me, so I decided to open a new one. So, the task is to find a force $F_{\mathrm{push}}$ on a desk which is leaned for an ...
0
votes
2answers
337 views

Direction of friction when a car turns

When a ball moves to the right, friction acts to oppose the motion, in other words, to the left. However, when a car travels around a bend, the friction acts in the perpendicular direction to the ...
2
votes
2answers
164 views

How is it possible to move something without completely lifting it?

For example, let's assume a chair here: It can be "slid" across the force if we use minimal upwards force, but not enough to actually "lift" the chair. Why should it move? Here's a better example: I ...
-3
votes
1answer
42 views

Acceleration on an inclined rail [closed]

I have to use $\vec{P}+\vec{R_N}+\vec{F_f}=m\vec{a}$ with $\|\vec{F_f}\|=\mu\|\vec{R_N}\|$ to express the acceleration as $$a_{x'}=g\sin\alpha(1-\frac{\mu}{\tan\alpha})$$ The configuration is (sorry ...
-1
votes
1answer
3k views

Rope tension between two objects [closed]

Let me explain the picture just to make sure. Object with mass 2 kg is being pulled with a force of F = 14.4 N. The whole system has an acceleration of a = 2.8 m/s^2. The friction coefficient ...
0
votes
3answers
101 views

$P\sin(\alpha)$ and not $\sin(\alpha)/P$?

Why is the force parallel to the surface that pushes the object $P \sin(\alpha)$ and not $\frac{\sin(\alpha)}{P}$? I didn't understand when they showed me it. can someone give me an answer in full ...
0
votes
1answer
414 views

Direction of friction in case of a rolling sphere

Suppose a ball rolls on a ground .obviously it is friction that helps to develop the required torque.Hence I find the direction of friction by pointing out the direction of rolling of the ball. But is ...
-2
votes
3answers
329 views

Why does a bicycle come to rest after travelling a distance?

According to Newton's law of motion, an object that is in motion will not change its velocity unless an external force acts upon it. In the case of a bicycle, if it is in motion with a certain ...
1
vote
1answer
375 views

Newtons Cradle, Collision Theory

It has come to the point in my computing program now where I have 5 swinging pendulums that are all modified at once by slider values. These values are drawn onto the from and passed through the class ...
-3
votes
3answers
178 views

Newton's laws of motion

According to Newton's laws, if net force is zero on a particle then the particle is at rest or in uniform motion, and if it is not zero then it is accelerating. So when a car moves on the road, ...
2
votes
3answers
278 views

Nature of frictional force

I was thinking about a situation where a person in standing on the ground with some friction. The frictional force is directly proportional to the normal reaction acting on him by the ground. Assume ...
1
vote
1answer
748 views

Calculating the frictional force

Here's my problem and the work I've done. The time is already past for me to submit the answer, but I want to know where I went wrong and why I was wrong. The 2-kg box slides down a vertical wall ...
2
votes
0answers
44 views

Impact of friction on a fallen body [closed]

If a body travelling at speed falls to the ground through an arc from a certain height (someone walking who trips, for example), how does friction of the ground surface affect the forces impacting ...
0
votes
3answers
86 views

Is it possible to reach the edge of a room if there isn't any gravitational acceleration?

Consider that a large room(an indoor badminton court) is orbiting the earth with a person floating exactly at its center without any relative initial velocity. Consider that the person has no ...
0
votes
0answers
26 views

Static friction greater than kinetic friction [duplicate]

Please explain why static friction is greater than kinetic friction logically. Speak about it microscopically and tell what does happen on surfaces of objects by considering electromagnetic force ...
-4
votes
2answers
2k views

How much force needed to push a car on neutral? [closed]

The car is a 2002 Toyota Corolla SE I have in my garage on a stone surface, I.e., the floor itself. What I want to know is how to determine the force needed to get it in motion at all. The curb ...
-1
votes
1answer
89 views

Force-Weight Pinewood Derby Car [closed]

Force-Weight Pinewood Derby Car. I'm trying to make a fast derby car. I was wondering if I could make a car that can drop/eject weight once it comes off of the incline. Would that increase speed or ...
5
votes
3answers
833 views

Why do we take small steps while walking on ice?

When we walk on ice we should take small steps. Small steps ensure: a.)larger friction. b.)small friction. c.)larger normal force. d.)smaller normal force. The correct ...
-3
votes
1answer
273 views

Question on static friction [closed]

This is the question, and the answer is given as 2). Now my basic doubt is, are they asking us the direction of the total contact force on the object by the floor? Or, are they asking the direction ...
1
vote
1answer
363 views

Mechanics question (a block on top of a block) [closed]

This question is very similar to this one here. A block of mass $m_1$ is placed on another block of mass $m_2$ lying on a smooth horizontal surface. The coefficient of friction (static and ...
-2
votes
1answer
262 views

Question on friction [closed]

Please look at the figure carefully. The question is written, and one has to match the two columns 1 and 2 given under "choices and explanation". Please tell me if I am really wrong, i.e. would you ...
5
votes
4answers
356 views

Comparing Static Frictions

In this figure, which of the static frictional forces will be more? My aim isn't to solve this particular problem but to learn how is static friction distributed . Since each of the rough-surfaces ...
0
votes
3answers
176 views

Smallest force to move a brick

Having a brick lying on a table, I can exert horizontal force equal to $\mu m g$ to a middle of it's side, and it will start moving (assume $\mu$ is the friction coefficient). However, can I make the ...