Questions tagged [forces]

This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use the [particle-physics] tag for decay channels due to forces and [newtonian-mechanics] or one of the other subtopics of [classical-mechanics] for the dynamics of classical systems.

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48 views

How does friction accelerate a car after rest?

If a car moves using the friction force from the rotation of the wheels, shouldn't a car be unable to accelerate immediately after the car is at motion, since there will be a friction force of equal ...
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Friction is also a conservative force?

$\color{red}{Warning \; ⚠️}$ :- This question is quite long and needs proper attention to the words used. I have asked a recent question about how spring force is conservative and in that I learnt ...
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Newton's 3rd law and Propellantless Propulsion

I was thinking lately about a potential misunderstanding regarding Newton's $3^\text{rd}$ law and the supposed impossibility of creating a device that moves by utilizing just internal forces (...
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How do pulleys redirect force?

Consider this setup of three blocks, in which you would like to find the acceleration of the 8 kg one: One way I've heard to solve it is to consider the three blocks as one system and look at the ...
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1answer
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Why is torque assumed to be constant?

Consider a spanner: I was doing calculations on how much torque would be applied on the bolt. To do this, I considered how much force was being applied at the full length of the handle. Then, I ...
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How can I relate torque with the tangential component of force times the radius?

In the book, Feynman lectures (Part 1, Section 18; 18–2: Rotation of a rigid body), the author says: $$∆W = (xF_y− yF_x)\Delta\theta$$ where $xF_y−yF_x$ is torque. He also says: Now let us consider a ...
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How much force does the wing beat of a large bird have?

For a large flying bird like the Andean condor, how much force in terms of lift and thrust does each wing beat have?
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Field between parallel plates [closed]

What is this parallel plate configuration? Book says The field it sets up is uniform meaning that at every point the magnitude and direction is same inside the field. A vector E is used in figures in ...
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Solving spring mass damper system having non ideal viscous damper [closed]

How to solve a spring-mass damper system, where the damper is nonideal (i.e. has mass). And, what can be an equivalent system for the same. (i.e. using a mass and ideal damper in place of a nonideal ...
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Is spring force really a conservative force?

Let us consider this picture. $\Rightarrow$ The first picture shows the initial position of the block when the spring is in its natural length and is kept on a smooth horizontal table. $\Rightarrow$ ...
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How does Newton's third law hold up when a block kept on a table breaks the table?

Suppose there's a block of some mass that is kept on a table. But, instead of staying at rest on the table, it breaks through the table. How does Newton's third law hold up here? If the block is at ...
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1answer
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Development of Propulsion system for standup paddle [closed]

I want to develop a propulsion system for a stand-up paddle even if it's already buyable. It should have the following specifications (extraction): max. speed: 7,2 km/h (2 m/s) Battery runtime: about ...
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Bodies falling at same rate [duplicate]

Why do bodies of different weight/ mass fall at same rate. Please do mention the mathematical explanation.
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General Newton's second law [closed]

Thank you, I apologize: next time i will use LaTeX. I ask to Vincent Thacker: I read your post but I ask if it is possible to get your last equation (or similar) in classical mechanics starting by d2/...
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Max's Crash and Gs

I was watching the British GP recently. Max Verstappen, who was initially leading the race, crashed out. Thankfully, he is all well, but he suffered a 51G shunt. I have been wanting to know how these ...
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What does it mean when physicists say a force is carried by particle? [duplicate]

I read things like “photons carry the electromagnetic force”, and “the electromagnetic field is composed of photons”. How does this work? I know a little math ( master’s degree) and am not averse to ...
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Is grain really a dipole?

Yesterday I was solving some electric field from resnik book and one of the solutions assumed a bee to be a sphere of charge $60 \;\text{pC}$ and the grain which sticks to it as a dipole due to ...
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Forces on a closed container that can electromagnetically suspend objects

If you have a closed container (without air or other fluids, only with the object inside) that can electromagnetically suspend or maintain (not like if the container walls are covered with a single ...
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1answer
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Tesla to Newtons Over Given Distance

I have a Neodymium magnet, for example, that has a magnetic flux density of $1.25 \;\text{T}$ and is 1 inch by 1 inch by 0.44 inches. I have a steel ball with a diameter of 0.5 inches placed 3 inches ...
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1answer
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Does the conveyer belt in this question change anything? [closed]

With what minimum velocity should the block be projected from left end A towards end B such that it reaches to the other end B of the conveyor belt moving with constant velocity v. The friction ...
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1answer
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Problems of Rotational Body at Uniform Speed [closed]

In this figure, $1.5 \;\text{kg}$ mass is connected to a $2 \;\text{kg}$ mass through a inflexible string. The $1.5 \;\text{kg}$ mass is on the surface of a table and through a hole on the table the ...
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1answer
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What is the centripetal force acting on the bob of a simple pendulum?

One might say that the tension force $T$ is the centripetal force, but $T$ has been already cancelled out by $mg\cos\theta$. So, either the tension force has been balanced/cancelled by $mg\cos\theta$ ...
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1answer
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How does down-wind faster than the wind (over-land) really work?

There has recently been posts on youtube where in a land based propeller/fan driven tricycle (blackbird) has been shown to roll faster than the wind that is behind it. The youtube channel veritasium ...
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1answer
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Fluid buoyancy why is $F_{\text{buoy}}=W_{\text{air}}-W_{\text{w}}$? [closed]

I am having trouble understanding the reasoning for a solution for a buoyant forces question. The density of a human body can be calculated from its weight in air $W_{\text{air}}$, and its weight ...
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What does the line integral of $\int\vec{s}\cdot d\vec{F}$ represent, where $s$ is the total displacement, and $dF$ is the force differential? [duplicate]

I recently started reading Feynman Lectures on Physics (Vol 1). I came across the formula for work done as, Work done is $\int\vec{F}\cdot d\vec{s}$ My question is: What does $\int\vec{s}\cdot d\...
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1answer
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Electric potential and fields

In electrostatics, what's the importance of potential, why can't I just just talk about electric field and force one charge has? Also besides that it's the negative gradient of electric field, is ...
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1answer
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How much weight $w$ is needed to keep the lever balanced? [closed]

Imagine here's a strange lever on the right side, there's weight $W$ sitting on an arm with the length $L$ on the left side, there's the L shape thing attached to the end, marked as blue in the ...
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1answer
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If two cubes with different mass but similar size fall from the same height in the presence of air resistance, which reaches first or is it the same?

Basically if the two box of same volume but one is heavier than the other which falls to the ground the first in the presence of air resistance ?
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Addition of velocities vs. Addition of forces

Imagine two strings tied to a box. Case 1: Two strings are pulled with the same $u$ velocity. The box will also move with velocity $u$. Case 2 : Tension along $\text{a}$ string is $T$. Therefore ...
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1answer
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Question about moment with two springs and one weight

The answer to this question is C. I got to it by realizing that if the weight is moved away from the pivot then it will produce an anti-clockwise moment which will cause X to decrease and Y to ...
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1answer
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What is the difference between elastic force and restoring force?

Elasticity is the ability of a material to return to its original shape after being stretched or compressed. When an elastic material is stretched or compressed, it exerts an elastic force. The ...
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3answers
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In what frame of reference does friction exists?

What is friction? Wikipedia defines friction as: Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. But forces are ...
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Can we resolve tension force into components for net force?

When solving certain questions , I noticed that in some places we take component of gravity along the string while in others, we take component of tension along gravity, I think that both of these ...
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How should I produce an equation for coefficient of static friction in the vertical axis?

I am currently working on the observation of the relationship between the weight of blocks and the inward force required to sustain the row of blocks. This is similar to the other posts from this site ...
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4answers
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Friction on a car

I wanted to ask why doesn't the car move on a frictionless surface. Suppose you are on a frictionless surface When you press the accelerator the wheels start rotating and apply a force to the ground. ...
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2answers
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Do we consider all the normal forces on a body while finding the friction acting on a body?

Case 1: Three blocks are being pushed by the force $F$. The horizontal surface and surface between blocks 1 and 2 are smooth. Only the surface between blocks 2 and 3 is rough. We did not consider the ...
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1answer
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How is my book doing what it's doing? [closed]

This is the stem. I'm concerned with the answer to d. First of all, the book doesn't specify what the two processes are, but I think the first process is, lifting each cube individually and stacking ...
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2answers
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Symmetry due to Newton's Third Law in the proof of Virial Theorem

Source: An Introduction to Modern Astrophysics This is from the proof of Virial Theorem. In the above picture's second equation, how the first term is zero due to symmetry from Newton's third Law? I'm ...
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2answers
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F1 car spin direction when losing traction

In this video at 0:19, the car on the right drifts too far onto the grass and ends up sliding to the left/anti-clockwise from top view. My initial instinct before the spin would be that car would spin ...
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Example for velocity being inversely proportional to force

We know that force is inversely proportional to the velocity when power is constant. Can someone provide me with a real-life example where an increase in the net force acting on a body actually ...
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1answer
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Should I take $g$ as positive or negative when calculating forces?

This is a question from the Fundamentals of Physics Textbook. My approach regarding this problem is that since that there is no acceleration ($\vec{a} = 0$), the net force ($\sum\vec{F}_{net} = 0$) ...
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Is Newton's Third Law valid in a frictionless surface?

When we walk on ground, we apply a force on the ground obliquely. The friction part of the reaction force from the ground on you, will prevent you from slipping. On a frictionless surface, as there is ...
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1answer
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Equations for force exerted on each of two cranes by a slanted cargo as a function of the angle it makes with the ground

This paper I'm reading on advanced rigging gives me the following picture: there's a cargo connected to two cranes. There are $L$ meters between the two connection points: $A$ meters between the ...
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A comparative study between individual blocks to one long block

In relation to two previous discussions about Newtonian mechanics first asked by esdoublef Free body diagram on a rack of wooden blocks and afterwards silverrahul, Horizontal Rack of blocks revisited ...
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Doubts about the strong and weak versions of Newton’s third law

I was going through some assertion and reason questions. (a) Both A and R are true, and R is the correct explanation of A. (b) Both A and R are true, but R is not the correct explanation of A. (c) A ...
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Normal Force in Elevator

I've recently been studying Newton's laws of motion and came across this example of apparent weight in an accelerating elevator. Taking the upwards direction as positive, when the elevator is ...
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Newton's momentum and power from the 4-force or Minkowski force

How can I get Newton's momentum and power from the time and space component of the 4-force at low speeds?
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Is it possible to calculate bike needed leaning angle from steering angle?

For a bike steering with radius of curvature $r$, we have $$\theta = \arctan \frac{v^2}{gr}$$ but you need to know r. I want to calculate the leaning angle from steering angle. It should be just ...
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2answers
59 views

A mathematical analysis of a single fixed pulley

I think Physics stack exchange is correct for this. Suppose we take a simple fixed pulley like this: Suppose the string is inextensible, massless and strong. One end of the string is connected to ...
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3answers
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Intuition regarding tension and its application in the case of a simple fixed pulley

This is what I comprehend as the tension of a string: Suppose we take a string suspended from a rigid support. If a weight $w$ is suspended on it then, it will exert force downward due to the force of ...

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