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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 [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or one of the other subtopics of [tag:classical-mechanics] for the dynamics of classical systems.

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Is it possible to use laser-like technology to create effective force field?

By laser-like lechnology I mean a coherent ray of particals or waves with the same amplitude/energy. This ray would be emited on limited distance (lets say 2meters) where it will be absorbed by ...
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1answer
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Does it make any difference for robots with motors, to use a lever to pick up things compared to usual picking up?

The force required for a human to pick up a box would be less if he uses a lever. Even though the total mechanical energy required is the same, one job is easier because human muscles operate more ...
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1answer
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Which one is easier, pushing downwards or pulling downwards?

Imagine we have a fulcrum, one side is us and one side is a 20kg weight. Which one is easier, to push our side's plate downwards to make the other side move upwards, or to lay under the plate and ...
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Derivation of friction in interleaved phonebooks

Trying to understand the simple model in https://arxiv.org/abs/1508.03290, describing the friction between the pages of two interleaved phonebooks. Specifically I don't see how to get Eq. 1. Here's ...
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3answers
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Why doesn't the Earth accelerate towards us?

According to Newton's third law of motion that states that every action has an equal and opposite reaction. So, if the Earth exerts a gravitational pull on us (people) then even we should exert a ...
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1answer
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Problem on force components [on hold]

In this problem, is the direction of tension(725N) shown in the free body diagram correct? Wouldn't such a direction lead to compression instead of tension.
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1answer
33 views

How is the normal force on a banked track larger than gravity?

The formula of the vertical force of an object that is not accelerating up or down on a banked curve is: Ncos(θ) = mg There is also a centripetal force component which shows that the normal force is ...
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2answers
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Solving elastic 2-dimensional collision problems where the resultant angle is not provided [on hold]

Having real trouble with the question below that is part of my engineering course. I've sussed question 6 but making no headway with Q7. A ball of mass 0.2 kg collides elastically with a heavier ball ...
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0answers
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What is the possible value for $A$ and Stress? [on hold]

So I'm trying to attempt this question, I've a paper tomorrow so I came here for a quicker answer, what I've tried already is considering that it can withstand 4kN from both sides but then total ...
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0answers
23 views

Rocket triggering problem [on hold]

If a rocket is to be sent to a body moving with a velocity of 10 m/s from a body at rest at a distance of 1km, if the acceleration of the rocket is neglected and it is moving at a velocity of 50 m/s, ...
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0answers
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How to generate force with air pressure [on hold]

I am trying to figure out how to generate a substantial force for a short period of time by releasing pressure in a small high-pressure air tank. A rough estimate of the force required is 40 ...
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2answers
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Are there such things as internal-external forces?

An example of an internal force is the tension in the spring of a harmonic oscillator. An example of an external force is the gravity on a pendulum. Are there any forces that are both internal and ...
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Forces and loads on linkages [on hold]

Hi All, The attached image shows a linkage mechanism with 2 parallel bars pivoted to a fixed base. The lengths of the the bars are equal. A connecting linkage and gears are used to connect it to a 3rd ...
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1answer
28 views

Time taken by falling body and Force via pulley? [on hold]

Hi guys, I have 2 simple questions. If you refer to the image you can see 2 figures. In Fig.1, I managed to calculate the time taken for a falling body via SUVAT. But I want to know how to calculate- ...
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5answers
73 views

Why does a point mass make a certain angle with a force exerted on it?

In real world, I see that if I hit (physicall speaking exert a force on)a marble or billiard ball properly (I think in its center of mass) it goes in a straight line with the force which means the ...
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2answers
44 views

What is the force of friction on the body? [duplicate]

This might seem like a stupid question, but my instructor could not give a straightforward answer. If a body is kept in contact with a completely vertical surface i.e. right angle to the ground, and ...
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1answer
49 views

What are some differences between electric force and gravitational force? [closed]

What are some differences between electric force and gravitational force? I mean, electric force is stronger, and electric force can be neutralized, but what else is there?
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2answers
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Why isn't the work done on the spring encapsulating this idea?

We know that work done ON the spring is given by the integral $$\int kx \, dx =\frac12kx^2$$ if we start from $x=0$ .But what if I apply more force on the spring.Wouldn't I be doing more work on it? ...
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15answers
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Which specific law of physics is broken by the “double jump”? [closed]

So, there's a cliche in computer gaming known as a "double jump". This can be described as: A character jumps from a solid surface, and then is able to extend their jump by carrying out the jump ...
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1answer
713 views

Physics of a punch

So I have odd question revolved around karate and would love to know if my physics assumptions are correct. Basically I would like to know what equation to use to calculate the force of a punch when ...
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2answers
72 views

How Does Gravitational force work on Light? [duplicate]

m'=$m_0/\sqrt{1 -v^2/c^2}$ How Will the gravitational force work on Light ?
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1answer
32 views

No standing wave at high tension [closed]

Why transverse standing wave in a string is finished when there is a very high tension in string .......I don't know the reason if tension increases speed then why there is no wave
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1answer
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Negative Work done by gravity

When we lift an object from ground we say we did work on object . We also say that gravity has done negative work because we did work to overcome gravity . When we did work our chemical energy was ...
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0answers
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What causes Gravity/Gravitation? [duplicate]

What causes Gravity/Gravitation? We know that mass causes gravitational force which is a non-contact force but is there anything physical that leads gravitational pull. Here, by physical I mean ...
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0answers
49 views

If gravitation force varied with $r^{-3}$ instead of $r^{-2}$ what would happen to Kepler's laws [duplicate]

2nd law wouldn't change as it is LCAM. 3rd Law would change. But I'm confused about first law. Does any body under influence of any central force move in an ellipse?Can anyone give a simple proof/...
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1answer
37 views

Tension in Spring

When spring is within elastic limit the tension in Spring is equal in magnitude to force applied for deforming it but when it has reached its elastic limit and more force is applied so that it's ...
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1answer
38 views

How the object will fall?

If we push a regular object from a table ( take a cuboid ) , can you predict that whether it will turn while falling or not and what face of it will hit the ground . Like if you accidentally push a ...
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2answers
29 views

Are forces of gases intensive or extensive?

What am I wrong at in here: I read that pressure is an intensive property. According to this and to $P=\frac{nRT}{V}$, can this be true: $(1)$: When $V$ is constant, increasing $n$ won't increase $P$,...
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1answer
24 views

How to calculate the force of a fan

Let's say that we want to build a helicopter, if we want it to hover in the air then the pushing force of it's fan must equal the force of gravity but in the opposite direction, so how do we calculate ...
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2answers
46 views

Why does not the static friction produce heat and waste energy?

I have asked this question wrt this question. So I want to ask the static friction opposing not the motion of the field just helps the field to get the energy back so the work now why does not the ...
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1answer
27 views

Calculate the distance covered by a balloon in 10seconds [closed]

Here's my problem: A balloon starts to move upward from rest with acceleration. The balloon has mass of 500 kg and volume of 600 cubic meters. I am prompted to find out distance covered by the ...
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2answers
91 views

Frictional force on smooth surface [closed]

While walking on ice , one should take small steps to avoid slipping. This is because smaller steps ensure $A)$ smaller friction $B)$ larger friction $C)$ larger Normal force $D)$ smaller Normal ...
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2answers
45 views

Pressure being isotropic

We say pressure is isotropic. At any point in a fluid pressure acts equally in all directions, but pressure is perpendicular force per unit area so how can pressure be there in all directions as ...
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3answers
48 views

Internal forces in a system

Newton's third law of motion says that the internal forces in a system cancel out each other --- what is the system here? what can be considered as a system? and why do the forces cancel out each ...
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1answer
53 views

Resultant effect of orthogonal motion of electric charges

*If two charges are moving uniformly with parallel velocity vectors that are not perpendicular to the line joining the charges, then the net mutual forces are equal and opposite but do not lie along ...
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1answer
41 views

How do salt crystals evaporate in water?

Salt dissolves in water but when water has evaporated it is still there. What has happened to the salt in the water and why is it still there when water has evaporated?
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6answers
100 views

Potential Energy and Work [duplicate]

My physics textbook says when a rock is lifted gravity does negative work and increases the gravitational potential energy. My understanding of negative work implies energy is being removed when an ...
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0answers
36 views

Large objects in the universe sized by gravitational and electrical constants

In a famous talk (from 14:30 to 15:00) Nima Arkani-Hamed tells us that what "fixes the size of the earth" is the equilibrium between the gravitational pressure against the atomic pressure of the atoms ...
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2answers
32 views

Clarify Torque and static friction [duplicate]

I came to this problem and solved it but I don't fully understand how this works. The problem is: A 200lb man climbs to the top of a 20ft ladder that is leaning against a smooth wall at an angle ...
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2answers
70 views

Why cannot we go in outer space with constant speed?

Sorry if this question is very childish for experts here. This was the question I had in school and years later it has resurfaced. I did some google search but getting the same equations of ...
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0answers
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Gravity as a fundamental force [duplicate]

In Dr.Einstein's theory of General Relativity-- he goes to great lengths to explain how the force of gravity is merely an illusion and in the case of the falling apple-- it is the earth accelerating ...
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0answers
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Does multiple tensioning pulley affects the belt speed?

Consider a multiple pulley system with the main pulley(30mm) attached to the motor shaft and multiple tensioning pulley in different locations(all are 15mm), driven pulley of 15mm is connected to the ...
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1answer
57 views

What is the direction of the “normal force”? [closed]

What would be the direction of normal and friction forces when a rod is falling which was initially kept upright on a table?
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1answer
53 views

What's the normal force on a squishy ball on an inclined track?

In this article... https://billiards.colostate.edu/physics/Domenech_AJP_87%20article.pdf ...which analyzes rolling friction on a rolling ball, the author claims that the normal force on a ball ...
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2answers
35 views

How does gravitational attraction relate to weight? [duplicate]

I understand that gravitational attraction is the attraction of a particle by another particle or matter, which in this case is the earth. But I don't understand why this (gravitational attraction) is ...
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2answers
48 views

Does an object moving with uniform velocity require a force to maintain its motion?

How does a trolley move with uniform velocity on a long board which has one of this ends raised to compensate for friction? If the trolley was given a gentle push down the long board, won't the ...
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1answer
39 views

Electromagnetic Force vs Magnetic Force

I am confused between these two types of forces, what makes them different? For example, a moving ferromagnetic object in a solenoid that moves because of a magnetic field created. Which field would ...
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2answers
33 views

Calculation of the Impulse of the force

can we calculate impulse of the force acting on a particle for a time interval using using Newton's 2nd Law which is described as Force acting on a particle equals mass of the particle times ...
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3answers
61 views

What's the difference between gravitational attraction and weight? [duplicate]

What exactly is gravitational attraction? In my textbook it was quoted " all objects both tiny and large objects are attracted to the earth. This is known as gravitational attraction, or the force due ...
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2answers
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Floating of needle on water [duplicate]

An iron needle when placed horizontally on water, floats (sits) on the surface of the water. The phenomenon is usually justified as "surface tension". From what I understand, for the needle to float ...