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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stopping distance [closed]

if it takes a 4 door sedan x amount of feet to go from 65 mph to 45 mph (and i don't know how many feet that is) on a dry straight road, how many feet would it take for a large Mack truck ...
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57 views

Fading transition and rotation of and object in 2D

I'm looking for sources about I guess dynamics subject. The model I'd like to solve is reduced to a question of: How does a force applied on a certain point of an object results in both fading ...
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1k views

Newton's second-law word problems with coefficient friction [closed]

Here is an example problem: A sled of mass 50kg is pulled along a snow-covered, flat ground. The static coefficient of friction is 0.30, and the kinetic coefficient friction is 0.100. What force ...
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400 views

What is the angle of the string with the vertical?

A heavy uniform sphere of radius $a$ has a light inextensible string attached to a point on its surface. The other end of the string is fixed to a point on a rough vertical wall. The sphere ...
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1answer
184 views

Why doesn't pushing balls in a tube propagate the movement faster than the SoL? [duplicate]

Possible Duplicate: Is it possible for information to be transmitted faster than light by using a rigid pole? On one episode of QI they asked the question, "How fast do electrons move ...
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1answer
279 views

Force due to combination of free space and dielectric

I will make a generalized form of my question. There are two point charges $q$, $x$ distance apart. And there is a dielectric slab of thickness $t$ and of dielectric constant $K$. Should the force ...
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0answers
168 views

Hooke's Law and the shape of coils

I've learned in school that the force in a coil is $F=kx$, linear on how much the coil is stretched. Two questions: Is it always linear for every shape of a coil? Does it remain linear if we ...
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346 views

Slackline Jump Tension

So a slackline is basically a bouncy tight rope. I found a site that has a calculator for the tension of a static slackline ...
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230 views

Simple: What do these ballistic impact numbers represent?

I bought physics for game programmers, found here, today to study ballistic impact, but I'm confused as to where a few numbers are coming from. I'm basically looking to understand what the values ...
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1answer
106 views

More efficient far-future means of keeping the earth alive? [closed]

In about 7 Billion years our planed will be consumed by the ever-growing sun, life would have become extinct long before that. That means that in several hundred thousand years we have a deadline to ...
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232 views

Modeling the trajectory of a particle in an Electric field [closed]

[This problem has been resolved, sorry for posting in the wrong forum!] (I was trying to model the trajectory of a particle in an electric field.)
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2answers
1k views

Infinite Atwood's machine

I tried doing the following problem just for fun (please see the following link): (I'm not allowed to post the entire problem here since I'm a new user.) Here are my equations: ...
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2answers
5k views

Finding distance when the force is a function of time

I'm having trouble with this homework question A mysterious rocket-propelled object of mass 49.0 kg is initially at rest in the middle of the horizontal, frictionless surface of an ice-covered ...
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1answer
639 views

How do I find the force an object exerts on adjacent objects when I push on it?

Suppose that I have a situation like the figure below, with several circular objects in contact. I know: $\vec{A},\vec{B},\vec{C}$: the positions of the points of contact between circles $\vec{O}$: ...
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890 views

FPS to MKS usage issues

I'm currently taking a high school physics class and we're doing friction problems now. I've been doing the ones that use MKS perfectly well, but when the problems start to use the FPS system, I'm ...
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104 views

Physics behind 2 different wall kicks

I'm looking at a situation where a sprinter starts at some distance x from a wall. The goal is to sprint to the wall, hit it, and get back to the start as quickly as possible. There are two ways ...
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209 views

How do I find the acceleration of an object at a certain velocity if I know it's mass and terminal velocity? [closed]

I have a mass of 85kg and a terminal velocity of 46.7m/s. I think I correctly calculated the coefficient of air resistance(b) as 17.84 because I know that the Resistance force at terminal velocity is ...
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1answer
423 views

Where are the centers of mass for a baseball bat vs. a cricket bat?

My friend and I were comparing the rightness of a cricket bat versus a baseball bat for general violence purposes. (Eg, rioting.) Where are the centers of mass for these two instruments? Which would ...
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2answers
1k views

What, if anything, makes forces the “cause” and acceleration the “effect”? [closed]

We typically say that forces cause acceleration inversely proportionate to mass. Would it be any less correct to say that acceleration causes forces proportionate to mass? Why? (Note that the ...
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0answers
1k views

What is the maximum non-fatal force withstandable by a human being for a short period?

Assuming any (optimal) body orientation/position relative to the direction of force and mechanism of death. I'd be interested in a rough estimate of threshold force and a suggested mechanism of ...
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2answers
350 views

For a massless pulley moving upwards with acceleration, is the upward force equal to the downward force?

Imagine a massless and frictionless pulley with two weights hanging either side of the pulley by a massless string. Like this except not attached to a ceiling Rather than being fixed to a ceiling, ...
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3answers
538 views

Proof that a force applied to the center of mass is the same as force applied off-center

There is a similar question that gives a bit of an explanation, but little mathematical proof here: force applied not on the center of mass I would like mathematical proof that shows that the ...
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1answer
262 views

A block, a string and Newton's third law

So this is a general force diagram of the system shown. My question is, according to the third law, if the block is exerting a force of magnitude mg on the thread in the down direction, then the ...
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3answers
510 views

Why is it easier to go uphill on a lower gear?

In cars as well as bicycles, when we are on a lower gear, the driving wheel (the one on the wheels) has a bigger radius compared to when on a higher gear. So on a lower gear the bike/car would move ...
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3answers
307 views

What is the use (/ meaning) of $F =ma$? [closed]

I have noticed that Euler's formula for force is useful with a couple of natural forces (at distance), like gravity, that can follow a body any length. If you consider the most common occurrences of ...
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2answers
525 views

Why do we say that in Coulomb's law the force is proportional to $\frac{1}{r^{2}}$ and not $\frac{1}{r^{3}}$?

I am going over Coulomb's law and there is something that is a bit confusing for me: According to Coulomb's law, if I have a charge $q_{1}$ at a point $\vec{r_{1}}$ and a charge $q_{2}$ at a point ...
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7answers
441 views

Could Galileo ever prove that $g$ is the same for a feather and a hammer?

Do you think he could have possibly found a way to make a feather and a hammer touch ground simultaneously, as they should, according to gravity? Can you make up a device that avoids air resistance? ...
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3answers
120 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 ...
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4answers
13k views

Why is force described as rate of change of momentum? [closed]

momentum = mass * velocity Differentiating both sides leads to force = mass * acceleration since the mass doesn't participate in the differentiation as it is constant. Is this a sound ...
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6answers
1k views

Is gravitational force affected by intervening medium?

If we leave a iron ball and feather into the water, feather returns to the surface and floats or moves into the water slowly. On the other hand, iron ball (of certain mass greater than mass of ...
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4answers
414 views

Can there be energy with no force or energy with no power?

I think that both force (number of newtons) and power (p=ui(?)) implies that there is energy so we can't have force without energy and we can't have power without energy(?) But can there be energy ...
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3answers
281 views

A force's magnitude

In this question I asked about gravity and in the answers it came up that the magnitude is equal (of the gravity acting on the Sun and the of the gravity acting on the Earth) Does magnitude simply ...
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5answers
2k views

Acceleration is zero, for non-zero net force

I understand a problem like this has already been asked, but I have not found an answer that makes it clear. A force is applied to a box on a table(lets ignore friction), and the box moves with some ...
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2answers
272 views

2 bodies separated by a rope [closed]

Say you have two bodies connected by a "weightless" rope, one hanging from a ledge on a pulley (classic pulley problem). If the body that is on the surface and being pulled by the object hanging ...
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2answers
77 views

How to solve this pendulum problem using kinematics, not the principles of conservation of energy?

I have this question, because typically problems that can be solve using conservation of energy or just energy-related principles, can usually be solved sing kinematic equations. (At least is what I ...
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2answers
234 views

How to intuitively understand Newton's third Law?

Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body. Newton's third ...
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4answers
447 views

Why force $F$ is $ma$ but not $md$ or $mv$? How can I observe and understand “force” in real life?

As a layman, i can calculate approx "displacement" just by observing the moving object. And accurately by using a simple "scale". Similarly, again, I can calculate angle from origin by using ...
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2answers
1k views

What is going on in the system? How are the formulas `mg sin(x)` and `mg cos(x)` derived?

When a load is resting on an inclined plane, there is force $mg \sin(x)$ that's vertical to the inclined plane and force $mg \cos(x)$ horizontal to the plane acting on it like this: My textbook ...
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2answers
1k views

force applied not on the center of mass

When applying a force outside of the center of mass of the body, the body will get both linear and angular momentum. Right? Does the linear velocity from this force equal to the linear velocity from ...
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3answers
311 views

Action - Reaction pair, through photons

Here's an example to describe the issue Supossed a high power laser (eg a 100 kW laser, ie, electromagnetic weapons) is fired to a target, then it will receive energy and move. (and likely to burn or ...
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4answers
65 views

Using formula for work with distance of 0m [duplicate]

Consider this: Wind is pushing a huge rock towards me at with massive force at 2m/s. I push against the rock at equal force so the rock stays still. I am clearly "working" very hard, using a lot of ...
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2answers
142 views

Who plays the role of centrifugal force in an inertial frame of reference?

It is noteworthy to quote a sentence from my book, It is a misconception among the beginners that centrifugal force acts on a particle in order to make the particle go on a circle. Centrifugal ...
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1answer
195 views

What is the net force acting on a climbing man by the rope?

I am confused with determining the net force on the climbing man below by the rope. My analysis is as follows. Let the tension be $T$. As both hands hold the rope then there are $T+T=2T$ upward acting ...
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3answers
262 views

Joules to do something

If my very limited understanding is correct, then, not accounting for gravity: 1 Newton can move 1 kilogram 1m But, can 2 Newtons move 1 kilogram 2 meters? Is this because 1 Newton = acceleration ...
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2answers
426 views

Is the Lorentz force conservative? [duplicate]

Is the Lorentz Force acting on a wire, that has current $I$ in a magnetic field $B$ conservative? Or non-conservative? I understand that all the fundamental forces are conservative, am I correct?
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1answer
637 views

Ball thrown in a moving train [duplicate]

A ball is thrown upward in a train moving with a constant velocity. Where will it land? My intuition tells me that the ball will fall at my back. But my book says that it will return back to the ...
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1answer
114 views

In Newtonian pressure, what type of function is force?

This is pressure in Newtonian mechanics: $$P=\frac {dF}{dA}.$$ What does this mean? (Doesn't it mean that force is a function of area?) What type of function is force?
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3answers
248 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 ...
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3answers
3k views

Force with zero acceleration [duplicate]

If I apply a force on a body which is kept against a wall, then the body will not move. The body is not moving means that its velocity is zero, and hence its acceleration is also zero. According to ...
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2answers
5k views

Confused on how to properly use right hand rule

I am having trouble using the right hand rule properly and often find myself putting my hand in awkward orientations. I know you point your hand in the direction of $r$ and then point your fingers in ...