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 ...

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0answers
86 views

On the nature of forces in general relativity

*** EDIT: I understand that it's not wise to fixate on Schroedinger words, however their meaning still remains obscure to me. Besides this my question on the possibility to abandon the concept of ...
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1answer
25 views

Lorentz Force and Apparent Conservation of Momentum Violation Useful for Unidirectional Force?

My understanding is that the apparent violation of Newton's Third Law by the Lorentz Force necessitates a description of the system that describes the "missing" momentum as being absorbed/carried by ...
1
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1answer
47 views

Force felt by parachutist when opening the parachute [closed]

When falling down with air resistance, y-axis vertical (positive is up), x-axis is horizontal, we have that: $F_y=-mg-kv=ma_y$, where $k$ is the drag coefficient. Now if the man opens the parachute, ...
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0answers
45 views

Free body diagram of pulley

Is there any difference between the free body diagram of fixed pulley and movable pulley? I've read that both of the rope of fixed pulley and movable pulley have the same direction (both upwards or ...
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5answers
82 views

Solving for $r=0$ in an inverse square law

This occurred to me in thinking about Coulomb's Law for a spherical insulator, but obviously can be asked of any inverse square law force calculation. For example, all things on the surface of he ...
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1answer
59 views

How does Newton's third law work

This law states that to each action there is an opposite and equal reaction. and I understand that this is the law that Rocket thrusters are built on. they use the combustion of fuel to push out hot ...
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1answer
38 views

Why does the mechanical advantage of a wedge use the length along the slope?

Since mechanical advantage is concerned with force, shouldn't the mechanical advantage of a wedge be calculated using the length of the wedge that's parallel to the applied force rather than the ...
1
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4answers
89 views

Gravity and force

I have a question and am not able to answer it. Suppose you drop two objects from different heights. They are exactly the same shape, size and weight. Now we know that the gravitational acceleration ...
0
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1answer
53 views

when does Newton's third law of motion come into effect

I'm a bit confused about when does Newton's third law come into effect and when it does not. For instance, lets say i was swinging a YoYo in a vertical circular motion, I would obviously have to ...
1
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1answer
88 views

Distance from Earth where gravity becomes negligible

This is a basic little problem I thought up when trying to remember some physics, and I wanted to see if it's at all correct: trying to figure out the distance from earth where gravity becomes ...
-3
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1answer
61 views

Can you answer these two difficult vector questions? [closed]

Figure 1 1) Determine the value of FB. 2) Determine the magnitude of FA + FB. (I know that the answer must be in Newtons. But other than that, I've very lost on what to do next. Please help!)
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2answers
50 views

Does towing a car make moving it easier?

once i saw a diagram in some of my books , of a car being towed by a big vehicle that was sort of a truck. now today that i am studying work , that picture somehow popped in my mind. it looked mostly ...
0
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1answer
44 views

Force as a Function of Position

If given a velocity as a function of position, is force as a function of position just it's derivative times the mass? I'm given the following and I am not sure my above logic is correct: The speed ...
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3answers
92 views

Free body diagram in sliding blocks situations?

I'm confused about the motion on two blocks sliding one over the other when more that one force is acting on them. Consider two blocks $1$ and $2$, with different masses, with $2$ placed over $1$. ...
1
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0answers
31 views

How to predict a flight distance? [closed]

I conducted an experiment by varying the stretch length of a rubber band (angle is always constant) which resulted in different flight distance. My teacher told me to find an equation/law to explain ...
0
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4answers
98 views

When is the direction of the static friction negative?

i thought that the force of static friction exerted on an object is always going in the opposite direction of any other force exerted on the same object. however, this problem seems to disregard that ...
0
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0answers
54 views

Alternating current. Resultant force

I've just been wondering: In an alternating current, the direction of the current is constantly changing. This implies that the acceleration of the charge carriers is constantly changing (pos. neg. ...
0
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2answers
76 views

Why is a sphere easier to move than a box of the same mass?

Is it only because of the less friction involved or at there other reasons?
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1answer
21 views

What is the force that generated by a moving car on the road? [closed]

Foce or vibration on road surface are usually depending on the speed and the wight of the car.
1
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3answers
133 views

Free Fall with Air Resistance

Can somebody help me understanding why when free falling the force on the vertical axis is F= -mg-kv, where k is the constant of air resistance and v the velocity? Suppose the vertical axis is ...
1
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0answers
85 views

Why do trees sway?

Resonance can also occur in three dimensions (such as wind induced swaying) I tried to make a free body diagram (I know it is terribly wrong) to find the forces that causes the tree to undergo ...
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2answers
60 views

The relation between acceleration and inertial force

Acceleration causes inertial force, and it is not relative, but why? What is the reason for feeling inertial force by acceleration?
0
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2answers
34 views

Dynamical friction force

Let we have a ladder leaning on the wall. Initially we hold the ladder and as soon as we release it the ladder starts to slide. My question: during the slide, are the friction forces at both ends ...
6
votes
2answers
310 views

How much upward force due to ground vibrations does the Earth exert on you?

Say you're walking by the highway and you can feel the vibrations of cars moving along. How would you approximate the force that the ground is exerting on your feet due to these vibrations?
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0answers
37 views

What is the magnitude of a collision force?

First off, I want to clarify that when I refer to collision, I mean the situation in which two particles cannot be at the exact same position in the space. When two particles get closer and closer, ...
1
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2answers
46 views

How paper strips get electrified?

Why paper strips get electrified when we iron them? I have learned that when two insulators are rubbed then they gets electrified but in case of ironing a paper the iron is a conductor. Will rubbing a ...
0
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1answer
51 views

Laws and Intuition for physical problems

So I've been reading the book 'Feynman: Tips on Physics' recently and in chapter 2 (the book is available for free online) he works out the answer for this problem using his intuition rather than ...
0
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4answers
60 views

How to determine the direction of friction force on FBD?

I am working on the following problem: Note that 0.5*N is the force due to friction pictured in the FBD. When I try to solve this, my intuition is to draw the friction force upwards rather than ...
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2answers
57 views

Im learning Work-energy theorem, this question popped into my mind about Force applied and displacement

I know a lot but I'm not sure, I'm guessing if $400J$ of work done on a 800 Newton object, if I'm correct, $400N$ to $800N$..that is $.5 m$ displacement, so by $W=∆KE$ why do I get $200J$? I was ...
2
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1answer
44 views

Minimum Tension Force Resistance, Chain Links [closed]

Say we have a chain made up with 10 metal links. By pulling on both ends' links in opposite directions, we apply tension force of, say 100 N. For the chain to remain unbroken under this tension, ...
1
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0answers
11 views

How to calculate force on impact after free fall in water [duplicate]

I'm trying to calculate the force of a man falling from a bridge into water below. Thus far I've calculated everything except for the force he would experience hitting the water. Would I need to do ...
0
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0answers
28 views

How to measure the magnetic moment of a bar of magnet?

I'm working on something and I need to calculate the force which is exerted on a magnet when it's put in a magnetic field I know the magnitude of magnetic field. So, the only thing I need is to ...
0
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0answers
38 views

Solving propulsion force of water rocket

As a note, I am not a physics student, although I am familiar with many physics concepts and calculations. I am trying to calculate the force of the thrust of a water rocket. I started with the ...
0
votes
0answers
34 views

Friction forces on car wheel

I know that frictions means a lot for car wheel. I've been looking all around a lot and trying to figure all out. I have found out about Coefficient of friction depends on slip ratio(which I am ...
3
votes
2answers
107 views

When a rocket or car is accelerating is the air in it going backwards or not?

I'm not sure but when a car is accelerating is the air in the car pushed backwards or not? If so why did Einstein say that there is no way of finding out (besides tidal effects) the difference ...
0
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1answer
76 views

How to calculate impulse force of body hitting water?

I'm calculating the force of a body hitting water from a high height. So far I've figured out the velocity at the time of collisions would be 40 m/s. The body is 78 kg. I seem to need the time it ...
0
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0answers
37 views

Centripetal Force Solving

I was recently learning about centripetal force when I came across a problem, I felt with my calculations. I re-watched the video, and the answer seems inadequate. The problem involves a bicyclist ...
0
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0answers
18 views

Air Powered Vs. Water Powered Rockets [duplicate]

I was looking online to find a comparison between purely air powered rockets, and water/air powered rockets, but could not find any. To clarify, a "water rocket" is filled partially with water and ...
0
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2answers
44 views

How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?

I'm practicing mechanics, and I had to resolve the following forces perpendicularly to the inclined plane in order to work out the reaction force (plus the weight of the ball) But I cannot tell ...
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1answer
26 views

Electricity problem [closed]

• Two small metallic spheres, each of mass 5 g, are suspended as pendulums by light strings from a common point as shown in Figure. The spheres are given the same electric charge, and it is found ...
50
votes
8answers
14k views

Short of collision, can gravity itself kill you?

Imagine that you are falling into object with huge gravity (i.e. black hole) that does not have any atmosphere. The question is - before you hit the ground, can the gravity itself (which would be ...
0
votes
1answer
73 views

A child swinging on a swing in sitting position and then stands up

I have one doubt which is that while swinging in sitting position if I all of sudden stands up on that sitting position and then started swinging with that same energy then does my time period will ...
0
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4answers
93 views

What are “Force Carriers”?

The concept of "force carriers" is hard for me to understand. I can understand "energy carriers". I can understand mass x acceleration but I can't see how this applies. Does anyone have a ...
0
votes
3answers
79 views

$F\cos\theta$ is not proportional to $d\cos\theta$?

If I’m working in two dimensions and I wanted to calculate the net electrostatic force on charge C, where charges A and B are stationary, of the same charge, and placed on the y-axis equidistant ...
1
vote
1answer
93 views

Are gravitons affected by the force of gravity? [closed]

1) Every particle, including photons, is affected by gravity. Would this be true for gravitons as well? 2) Gravitons should always move at the speed of light, so, if photons are red-shifted while ...
-1
votes
6answers
137 views

People went down two different length slides end up at the bottom at the same time [closed]

Discussion I am having: If there are two slides that are at the same height. One slide is 100m long and the other slide is 200m long. The endpoint and start point are the same displacement. In ...
0
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2answers
141 views

A classical explanation of why there is a speed limit in the universe [closed]

The question is - is there any flaw in this explanation, or it is the right explanation in general language? Let me break the explanation into two parts - Why there is a certain speed of ...
2
votes
2answers
140 views

What is the Benefit of Plotting a Log of Net Force vs. Log of Acceleration Graph?

In preparation for a quiz, I've been going over a set of sample questions. One question in particular asks that if I am to graph the logarithm of the horizontal net force of a system vs the ...
10
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3answers
304 views

How can a bowling ball curve in both directions?

There is a popular video on facebook that I just don't understand. A man spins a bowling ball very fast then slightly taps it down the lane. Somehow it does half of a figure eight, curving around two ...
3
votes
6answers
146 views

When we write that $F = -\nabla V$ , what would happen if we ommit the (-) minus sign

I have had this question for a long time. In classical mechanics, if we choose $\mathbf F = -\mathbf \nabla \, V,$ with the minus sign, we can proof the work - kinetic energy theorem. What are the ...