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 ...

learn more… | top users | synonyms (1)

1
vote
0answers
9 views

Calculating Time to reach a given velocity knowing force of thrust

so I am working on a physics problem for a class I am taking. The problem is as follows: -A rocket, weighing $4.36\times10^4 N$ has an engine that provides an upward force of $8.90*10^5 N$. It reaches ...
0
votes
2answers
35 views

Ice at zero gravity

I wish to know the behavior of ice at zero gravity, sound at zero gravity. How ice will behave when melted and how sound will break a closed glass at zero gravity vs g on earth? Thanks
0
votes
0answers
26 views

Infinite force between two point charges as $r$ approaches 0 [duplicate]

According to coulombs law the Force experienced by two point charges increases with the inverse square of their separation. This would imply that at distances approaching 0, the Force approaches ...
1
vote
1answer
14 views

Single fundamental force at Planck epoch?

It is hypothese that after big bang when universe is a Planck time old, the 4 known fundamental forces used to be equal in strength or perhaps there existed single fundamental force before splitting ...
2
votes
0answers
20 views

What kind of forces would follow only the second part of shell theorem?

General expression of a force which would cancel out inside a uniform hollow shell. What about any closed surface?
0
votes
3answers
38 views

How does $p=fv$ hold when $v=0$ and an engine is working?

Standard high school equations: Work = Force x Distance Power = Work / Time = Force x Distance / Time = Force x Velocity When a space rocket takes ...
2
votes
1answer
20 views

Contact forces and the structure of matter

Textbooks on introductory physics depict friction force as a result of interatomic forces. Matter is made of atoms and those atoms have eletric bounds. In turn, those eletric bounds are responsible ...
2
votes
1answer
27 views

Calculating wind force and drag force on a falling object

I'm trying to numerically integrate the motion of an object (say, a falling vertical cylinder). Here, there's a drag force: the wind "acting" on the body (presumably adding horizontal velocity) and ...
1
vote
0answers
29 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
1
vote
1answer
35 views

if you have an object on an inclined slope, by applying a horizontal force would you be able to lift the object from the slope?

I am programming a free body force diagram and as part of it a am allowing the user to adjust the angle of the plane and apply a force to an object on such plane at any angle to the horizontal. My ...
1
vote
5answers
69 views

Which one acts first: friction or tension?

I have a block kept on a rough surface with a string attaching it to the wall. I pull the block opposite to the string with a certain force $F \leq \mu mg$ where $\mu$ is the coefficient of friction ...
1
vote
2answers
55 views

Force when distance between charge is zero

According to coulomb law $$ F = \frac{q_1q_2}{r^2} $$ I want to know what happens to force when $r=0$. If $F \to \infty$ then the charges can't be separated! But if an unlike charge of higher ...
0
votes
1answer
40 views

Lead bullet vs a Rubber bullet?

Our teacher says that rubber bullet is more effective than a lead bullet for knocking down a bear/human/whatever. He says that change in momentum for rubber bullet is greater than that for lead ...
-2
votes
0answers
31 views

Why doesn't a nuclear reactor's filament deform?

Why doesn't a nuclear reactor's filament deform? The filament in the core of a nuclear reactor is usually made of uranium rods. So in the nuclear reactions the neutrons constantly move from filament ...
25
votes
8answers
3k views

Does it take more energy to open a door when applying force close to the hinge?

Assuming an ordinary hinged door (without any springs), would it take more energy to open it when applying force in the middle of the door (point b), rather than at the end of the door (point a), ...
0
votes
2answers
38 views

Why taking components of a component of a vector is invalid?

Suppose there's a force $F$ of magnitude 10 newtons in the direction of positive y-axis acting on a particle A. I know that the particle would not experience any force in the positive x-direction ...
1
vote
3answers
125 views

Are circles stronger than triangles?

I've often herd in engineering that "there is no shape stronger than a triangle". I also recall that arches are very strong shapes as well, which can be crudely described as a ...
2
votes
0answers
31 views

Tensions in a rope [duplicate]

If two tensions are acting on a rope such that they are equal (each is 10 N) and opposite (180 degrees) then what will be the total tension in the rope? I cant seem to figure out if these two will ...
-1
votes
0answers
23 views

Forces in equilibrium [closed]

A homogenous beam OA with the length 4a and the mass m can rotate i the vertical plane around a horisontal axis through O and is kept in equilibrium by a wire attached in the points A and C going ...
0
votes
1answer
25 views

What is a “Reversed Effective Force”?

I have some confusion about the "Reversed effective force" as it appears in the derivation of D'Alembert's principle. First I have sources that seem to be contradictory. ...
-1
votes
0answers
43 views

Determine center of mass! [closed]

See the very funny figure. I have determined the mass of center in the x-coordinate to $r/4$ but I don't know how to get the y-coordinate. The key says it's $- r/ \pi$ but I can't see how to get ...
0
votes
1answer
37 views

Good way to compute the force of a hammer blow?

What is a good and easy way to compute and/or measure the force of a hammer blow, not using any fancy or specialized equipment? If the hammer is swung by hand through an arc, it is not obvious to me ...
4
votes
2answers
41 views

First-principles derivation of cutting force

I know that the amount of force required to separate a material from itself is linked to the surface energy of that material. However, looking at just the surface energy laughably underestimates the ...
0
votes
2answers
91 views

Maximum Extension of a Spring [closed]

In the given figure: m= 5kg, F = 30N, K = 700N/m In the figure shown above. the surfaces are friction-less. The blocks are initially at rest and the spring is initially in its natural length. What ...
1
vote
1answer
140 views

How did Feynman prove that energy cannot be extracted from electric field?

In the Feynman Lectures, vol. II, chapter 4, Feynman discusses electric potential and says: If we carry a charge from point $a \to b$, $$W = -\int_{a}^{b} \mathbf{F} \cdot ds.$$ Now, in general, ...
0
votes
1answer
37 views

If the cord has a breaking strength of 25.0 N, explain why the cord broke when supporting a load so much lesser than its breaking strength [closed]

A picture of weight 5.0 N is suspended from a hook on the wall by a cord. The tension of the cord is 7.07 N. It was found that the picture is hung too low on the wall and was adjusted by shortening ...
0
votes
1answer
38 views

Help calculating work done by stretching a wire [closed]

A wire of length 0.89 m and cross-sectional area 1.7 cm2 is stretched elastically by an amount 1.2 cm. By Hooke’s law, the restoring force is $−k\Delta L$. Calculate the work done in ...
1
vote
5answers
88 views

How to interpret that forces do not depend on acceleration?

I was told forces can depend on time, location and velocity, but never on acceleration. At first I thought this must be wrong, thinking of $F=m\cdot a$. But I think/hope I now got what was meant, what ...
1
vote
3answers
94 views

Does dark energy work like gravity, but the opposite way?

If a body has more mass gravity will exert a greater force on it. Does that apply also to dark energy? In other words, if a body has more mass, will it be affected more by dark energy? (that is, will ...
0
votes
1answer
77 views

Gravitinos the key to theory of everything?

Theory of everything The theory of everything aims to unite all the four forces of nature into one single elegant equation. Super-symmetry Super-symmetry is important as it explains the nature of ...
2
votes
5answers
191 views

How can static friction do work?

By definition, the work done by a force is $W = F\cdot d$, so how can static friction do work? Can this force move the body a distance of $75~\text{m}$?
0
votes
1answer
58 views

Confusion about average force applied over a time interval

If I understand correctly, the word average implies the average of forces acting during a certain time. $$F_{avg}=\frac{\int_{t_i}^{t_f}{F(t)\,dt}}{t_f-t_i}$$ The teacher gave us tasks with answers ...
0
votes
2answers
45 views

What guarantees that in a circular motion in a vertical loop, the resultant of the forces will always point to the center?

Here's what I know: If a body moves in a circular trajectory, then the resultant of all the forces must point to the center of the circle it describes in its movement. If a body moves in a vertical ...
1
vote
1answer
35 views

The force on the northern hemisphere

I am reading Griffiths' Introduction to Electrodynamics. On page 364, example 8.2 (4th edition), he calculates the force on the northern hemisphere of a ball with total charge $Q$ spread uniformly. ...
-7
votes
0answers
30 views

What will happen when an unstoppable force meets an immovable object? [duplicate]

I was thinking when this question came to my mind. What will happen when an unstoppable force meets an immovable object?
1
vote
1answer
48 views

Effect of Eath's rotation on a ball thrown upwards

Since the Earth is rotating it should have acceleration (in the sense that there is change in direction of velocity). So if we throw a ball upwards won't this acceleration affect its trajectory in ...
1
vote
1answer
45 views

Lagrangian formalism application on a particle falling system with air resistance

I have this problem, with a first-step resolution: $$...$$ So, I just don't know why they put the term $\frac{\partial F}{\partial \dot{z}}$ in Euler-Lagrange's equations. Why? I know that the ...
0
votes
2answers
22 views

Capillary action and its limitations

From Wikipedia Capillary Action Thus for a 4 m diameter glass tube in lab conditions given above (radius 2 m), the water would rise an unnoticeable 0.007 mm. However, for a 4 cm diameter tube (radius ...
2
votes
5answers
251 views

when an object is lifted (at a constant velocity) shouldn't the work done on the object be zero? [duplicate]

When I lift an object from the ground (at a constant velocity) I'm applying force on the object equal to its weight and the earth is also pulling it downwards with equal amounts of force. So if the ...
1
vote
1answer
33 views

Could satellites achieve orbit using current laser technology

My question is, could we, using current laser technology sufficiently scaled up, launch a lightweight, say a GPS navigation satellite, into earth orbit? The main objection to me is maintaining the ...
-1
votes
1answer
60 views

Throwing a basketball. What do I need to consider to hit a target? [closed]

This is a question that's been bugging me for some time now and the physics department at school is closed so yeah. Anywho, my question was, given a ball of mass .76, what forces would i have to ...
0
votes
1answer
44 views

How can I carry out this force summation? Control volume involved

I have a stationary jet engine on a test stand, like shown in the next figure: The control volume is indicated in the figure as a dashed rectangle, that has its left side far upstream of the ...
0
votes
1answer
21 views

Angular acceleration of two rods joined in the center - did I do this right?

The question is: The moment of inertia of a thin rod of length $l$ and mass $M$ about a perpendicular axis through its center is $\frac{1}{12}Mt^2$. The object shown consists of two ...
0
votes
0answers
11 views

Pressure change in throttling & flow rate reduction in a water circulation

If the pressure in a water pipe line is reduced from 7kgf/cm2 to 4 kgf/cm2, what is the % reduction in flow rate?
1
vote
2answers
46 views

Why am I getting that work it's always the same in both directions?

I'm studying electrostatic and I'm getting pretty frustrated because with the definition of work I'm getting that it's always positive and it doesn't make any sense. So here I have 2 positive ...
2
votes
2answers
132 views

Can we rigorously define force?

I'm looking to get rigorous definitions on which to base the important quantities in classical mechanics. To me a "rigorous" physical definition is an operational definition -- that is one in which ...
0
votes
1answer
36 views

Determining the force of a spring

How can I determine the maximum force a spring can release when it pops up? Is there even a formula for this?
0
votes
1answer
22 views

Resolution of force vectors

For example in a simple pendulum problem.. the forces that act on the bob are tension and gravitational force. but while the resolving the vectors to find T(tension) at any given angle x with the ...
0
votes
1answer
42 views

Force and initial height of thrown object [closed]

You stand at the earth's surface, and you throw a ball of mass m1 into the air perpendicular to the surface. Let g at the surface be 9.81m/s^2. You know two points (height:h1, h2 and time:t1,t2) of ...
0
votes
2answers
47 views

Question about a car on a banked turn with no friction

A popular physics page explaining how a car can make a banked turn even with no friction : gives the following free body diagram and then says In the vertical direction there is no ...