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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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12 views

Total force on a point charge?

I want to calculate the total force acted upon the negative charge in the middle of the circle by the 8 equal positive charges in the periphery. The positive point charge at the bottom is moving with ...
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Designing Circuit whose voltage is controlled by weight [on hold]

I'm really confused on part b of this question. I know what part a's answer is, and I get that -- 2(L-kF)/A But I just don't know where to start with the circuit. How do we know which components to ...
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Is there a reason why forces act a certain way?

I was just wondering if forces in nature just exist as they are or do they have a physical reason for acting the way they do, such as the restoring force and gravity. For example I understand that the ...
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18 views

Terminal velocity and distance traveled of a sphere in a liquid

I have actually done this question, but I think it's wrong. The terminal velocity I got was 6000 m/s and a distance traveled of approximately 4000 km. The question is: A sphere with radius R = 5.0 cm ...
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2answers
97 views

A bead on the wire loop

In my physics book there is a question which stated is as follows: A thin circular loop of radius $R$ rotates about its vertical diameter with an angular frequency $\omega$. Show that a small bead ...
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4answers
64 views

Can someone explain what is the force the ball will exert?

If a ball is falling under free fall then the force exerted by the ball on the ground would be $mg$. But that's not the case in real life ball would hit with more force. But when i draw free body ...
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12 views

horizontal rolling without slipping with constant force acting [on hold]

rolling without slipping ##question an ideal string is wrapped around a cylinder of mass m and radius r, which rotates about a stationary horizontal axis. the free end of string is pulled by constant ...
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23 views

How can the acceleration of a person on a zipline be calculated?

I was thinking one day about how a speed, or perhaps the acceleration, of a person riding a zip line could be calculated. I first started by thinking of an ellipse where the two foci were the anchors ...
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1answer
56 views

Finding two masses as one rotates about an axis, no givens

My Physics C class was given a lab today with little explanation, and many of us are having issues determining a solution. We are given this apparatus: We must find the masses of both objects m and ...
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A particle is observed from two frames $S_1$ and $S_2$

The frame $S_2$ moves with respect to $S_1$ with an acceleration a. The $F_1$ and $F_2$ be the pseudo force on the particle when seen from $S_1$ and $S_2$ respectively. My problem is, can such a ...
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1answer
96 views

Why is contact resistance proportional to $\frac{1}{\sqrt{F}}$ not $\frac{1}{F}$?

See pages 13-15 in "Electrical Contacts: Principles and Applications" for reference. Imagine the following system: Two flat, but rough, surfaces of the same finite area $A$ being brought together. ...
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7answers
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How does kinetic energy work in braking a vehicle?

Do the brakes have to do more work (ignoring air resistance) slowing a vehicle from 10 m/s to 8 m/s than from 8m/s to 6 m/s? Say a 1000 kg vehicle is moving at 10 m/s, it has kinetic energy of $$0....
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How to find acceleration with angles included? [on hold]

[![enter preformatted text here][1]][1]How do I find acceleration of an object if I have force, mass, friction, and there is 2 given angles (object and force)? I ...
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31 views

Forces active during sucking spaghetti [on hold]

2 years ago I presented in the "Forum of Physics" a subject that I titled: "Difference of pressures? ... Well I do not understand." The associated question was: What is and where is the force, or ...
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5answers
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Formulation of Newton's second law: $F=ma$ or $a=\frac{F}{m}$?

Assuming a constant mass, which would be best way of expressing Newton's second law? $F=ma$ or $a=\frac{F}{m}$? The most common way is the first one, but I feel more comfortable explaining it the ...
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1answer
32 views

Why don't all the bodies accelerate as all of them are brought into motion through a force?

Like in a Projectile, why isn't there an acceleration in the horizontal direction? I've seen things like there isn't any force acting (in the horizontal direction) but for the body to move there must ...
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2answers
61 views

What do we understand by a force being central?

Gravity is said to be a central force. But the resultant force field of multiple bodies is no longer central as it has many attraction points. My Doubts: Is the idea of a force being central ...
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2answers
68 views

Cross product in Physics [on hold]

The most famous cross product in physics is the one linked to Lorenz's force. In which other models that describe physical interactions is the cross product used? Are there other laws related to the ...
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52 views

Does string theory really associate 6 dimensions to electromagnetism & the nuclear forces?

1) I understand string (superstring) theory often ends up with 10 dimensions, 9 space-like and 1 timelike. Typically I read that these are all associated to space-time. 2) So, I was interested when I ...
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20 views

What downward forces will a ladder exert as it is lifted to be parallel with a wall from flat? [on hold]

Assume you have a ladder with uniform weight of 100 lbs and length of 20 ft. It is flat on the ground and one end is against an immovable wall. And a person with arms straight up has a foot to hand ...
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0answers
15 views

What's the force factor of the $n$'th locomotive in a multiple traction? [on hold]

Today I noticed how 2 Re 4/4 II locomotives carried freight. The term called to describe this is multiple traction (in this case ...
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3answers
698 views

Is tension always the same as centripetal force?

For example, if a ball is attached to a string and released from a vertical height and then pivots around a point to initiate circular motion, tension is equal to centripetal motion. If, on the other ...
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2answers
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What is the difference in the way a single rope and a double rope would behave under dynamic load?

Suppose I have a single rope attached to a fixed point via a load cell, which gives a number (in kN) based on the load it's experiencing. I take a weight (x) and attach it to the rope at a fixed point ...
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1answer
35 views

Force Applied but No Distance Travelled

Suppose I push on a wall with a constant force of 5 N for 10 s. The wall won't move and hence no work will be done on the wall. However, pushing requires energy. How can I find out how much energy I ...
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1answer
21 views

How to find the work of each force acting on a block? [on hold]

A push of 200 N moves a 100 N block up at 30º inclined plane. The coefficient of kinetic friction is 0.25 and the length of the plane is 12 meters. a. Find the work done by each force that acts on ...
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1answer
30 views

Analyzing Friction in Velocity vs time graph [on hold]

Let's say there's an inertial force F, which makes cart with mass m to accelerate and reach speed v0. And then, due to friction the cart starts to deaccelerate. If we were to graph the velocity vs ...
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21 views

Virtual Work and Arbitrary unit vectors

I was recently watching a lecture on MIT OCW where they were talking about Newton's Laws for a pulley system. The professor solved a problem pretty quickly using a method called virtual work. I tried ...
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2answers
48 views

A heavy ball on a thin sheet of paper

If we keep a heavy metallic ball on a thin sheet of paper the paper is torn and the ball drops. But according to Newton's third law of motion every action has an EQUAL and opposite reaction. So when ...
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6answers
66 views

Will a man falling from a great height and a man lying on ground exert same amount of force on the earth?

Suppose in a situation there is a man falling from a height, when he falls from a height and touches the ground then he applies some force on the ground which is equal to his weight, and in another ...
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3answers
38 views

Change of buoyant force as object moves deeper

When reading about Fluid Dynamics, I saw two questions that presented similar situations but had very different answers, and I'm trying to understand why, since they seem contradictory: A beach ...
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2answers
50 views

If a ball is kept on the table, then what forces are being exerted on it?

If a ball is kept on a table then there is gravity acting on it as well as a normal reaction force by the table on the ball. But as both the forces are being exerted on the same object i.e. the ball, ...
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2answers
39 views

How do we calculate the force applied by a ball on a wall which bounces back? [on hold]

If we have a ball which we throw toward a wall which touches the wall and bounces back then how will you calculate the force applied by the wall on the ball because the the contact time of the ball ...
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1answer
64 views

Find $v(t)$ and $x(t)$, How do I treat $δt$? [closed]

We apply a force to a particle with a mass $m$ and inicial velocity $v_0$: $$ F(t) = \left \{ \begin{matrix} 0 & \mbox{ $t<t_0$} \\ \frac{p_0}{\delta t} & \mbox{ $t_0<t<t_0 +\...
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2answers
29 views

Work done by a varying angle

I know that work done by a constant force is $W=\vec{F}\cdot \vec{x}$, and that work done by a variable force is $\int \vec{F} d\vec{x}$. However, how do you calculate work done by a varying angle?
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1answer
109 views

Newton's Third Law of Motion? [duplicate]

Newton's third law of motion states that every action has an equal and opposite reaction. But, on punching a wall, I feel much greater force than on punching an inflated balloon. So, what does it mean?...
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2answers
41 views

Where does the other part of the hydrostatic force go?

The hydrostatic force on the floor is $$F= \gamma \cdot h \cdot Area$$ for both the pipe and funnel. But, for the funnel there is so much more water. So, we expect the force to be higher for the ...
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1answer
165 views

Could theory of Relativity be overlooking a relationship between time and force? [closed]

Does Time dilation effect correspond to a property of the world that is suited to the term's "modulated force" or "force dilation"? It seems a simple truth. A modulation in the rate of force-driven ...
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2answers
37 views

Strange factor of 2 in Hooke's Law [duplicate]

I was working on a PGRE practice problem: A brick of mass $m$ falls onto a masses spring with spring constant $k$ from a height $h$ above it. What is the maximum distance the spring will be ...
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1answer
60 views

Why is it impossible to start or stop an object instantaneously? In what ways can a non-accelerating object move? [closed]

Why is it impossible to start or stop an object instantaneously? In what ways can a non-accelerating object move? I think this has to do something with inertia, but I am not exactly sure I fully ...
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2answers
58 views

Intuitive explanation to why force perpendicular to velocity results in circular path

I know in circular motion F is perpendicular to V. But I don't understand how this results in a change in direction and no change in speed ( which ultimately results in a circular path). In short, ...
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1answer
41 views

Does a normal reaction do work too? [duplicate]

On backflipping off a wall, the wall applies an equal and opposite force that pushes the person in the opposite direction of the applied force. Or, on simply pushing a wall, the wall pushes back. Does ...
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0answers
14 views

Calculate Force on Permanent Magnet from a Coil

I was wondering how I could calculate the force on a permanent neodymium magnet. For this setup, I have a magnet on a scale with a coil directly above it. The magnet and the coil repel each other when ...
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4answers
85 views

Why does body with continuous speed generate force?

So... sorry if the question seems a bit stupid, but it's been nagging me all day and I couldn't find an answer on the net. It goes like this: If a body, say, a car is moving with constant speed. This ...
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7answers
87 views

Why is work equal to force times displacement?

This is how I think of what work is.I am sure I am wrong somewhere because I shouldn't be coming to the conclusion that I am coming to.It would be helpful if you would point out where this conceptual ...
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3answers
52 views

What will be the force when you push a wall?

force is change in velocity times mass so if i push a wall there will be no change in velocity of the wall it will be in rest,acceralation will be 0, and so the force should be zero.So it means that ...
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1answer
45 views

Why doesnt my fist go through the wall? [duplicate]

When I punch a wall, Why doesnt my fist go through instead of staying at rest on the wall? What is cancelling out the force of my punch?
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1answer
34 views

Damped Oscillation and Period

In my school experiment, I wanted to measure the gravitational constant ($9.81 \ m/s^2$) by using a pendulum. If we take into account the damped oscillation (i.e. friction forces), does that affect ...
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5answers
171 views

Work done by friction in a complicated path [closed]

A block of mass $M$ is taken from point $A$ to point $B$ in a complex path by a force $F$ which is always tangential to the path. We also have coefficient of friction as $K$. What will be the work ...
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1answer
90 views

In a Bose-Einstein condensate, do the cooled particles lose weight? [closed]

If the elementary particles are cooled, they lose a weight?
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3answers
76 views

Reaction Force or Normal Force? [duplicate]

When we punch a wall our hand hurts... Do we feel the pain due to the normal force exerted by the wall or due to the reaction force?