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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4answers
135 views

The work done by running in a rectangle

This may be quite off-topic but please help me. Is there any work done when I run in a rectangle? I thought that the answer should be no. But my teacher says that we should calculate each side ...
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1answer
71 views

Falling metal cylinders more devastating than a nuke?

I just saw G.I JOE - Retaliation. In the movie the bad guys (spoiler alert) Could this device cause more destruction than a nuclear weapon? If so, how?
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1answer
95 views

Why is it easier to turn a heavy hanging object?

Assume if we had a 2 tonne weight placed on ground attached with a rope that we can use to turn the object around. It will immensely hard to turn that object around by pulling the rope. However, if ...
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1answer
750 views

The nature of the gravity force: Is it attractive or repulsive between positive and negative mass? [duplicate]

If negative mass is rotating around fixed positive mass, then what will be the nature of force and how?
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2answers
102 views

How come weight doesn't affect the rebound height on a net?

According to my text book two unequal masses, (80kg and 50kg) fall on a net and the work done by that net is calculated by $\frac{1}{2}kx^2$. This work is then transformed into kinetic energy for both ...
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1answer
380 views

Toppling of a cylinder on a block

A uniform cylinder rests on a cart.The height and diameter is given.coefficient of static friction is given.How can i find the minimum acceleration of block such that the block topples? Morever what ...
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2answers
92 views

Finding the value of velocity $u$ [closed]

A block of mass $m$ is pushed towards a moveable wedge of mass $\eta m$ and height $h$, with a velocity $u$. All surfaces are smooth. The minimum value of $u$ for which the block will reach the top of ...
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2answers
1k views

Direction of friction when a car turns

When a ball moves to the right, friction acts to oppose the motion, in other words, to the left. However, when a car travels around a bend, the friction acts in the perpendicular direction to the ...
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2answers
134 views

Can you justify force calculations using more than one of Newton's laws?

If an object is at rest on a flat surface I remember my school teacher would say, "By Newton's 1st law the normal reaction, R, is mg (mass x g)". Ok, sure this is fine because the object is at ...
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3answers
86 views

Is it possible to reach the edge of a room if there isn't any gravitational acceleration?

Consider that a large room(an indoor badminton court) is orbiting the earth with a person floating exactly at its center without any relative initial velocity. Consider that the person has no ...
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2answers
10k views

Finding the drag force (Air resistance force) for accelerated ball?

As you know if I want to find the force for an accelerated object I will use the law $F_o=ma$ so I can get the affecting force of it. But there is another force affecting against the object. It's the ...
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1answer
188 views

Why body starts moving when force is applied? [duplicate]

The recent question by m.buettner regarding self-inductance and its resistance to EMF Faraday's law - does the induced current's magnetic field affect the change in flux?, recalled me the ...
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1answer
285 views

Component of force field tangent to a curve

I recently had to solve the following problem: A force $F=10\hat x- 8\hat y$ is applied to an object that is constrained to travel towards increasing values of x along the path defined by $y=x^2$ ...
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2answers
6k views

Tensions And Pulleys With Masses

The problem I am working on is: "A block of mass m1 = 1.80 kg and a block of mass m2 = 6.30 kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = 0.250 m ...
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1answer
702 views

Understanding the math behind a falling object attached to a parachute

I'm trying to understand the mathematics behind calculating the total speed and force of a $40 kg_f$ object hooked up to a parachute, falling to Earth. From what I understand, the formula for this is ...
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1answer
1k views

Simple derivation of the tension of a cord on a suspended mass

Just wanted to disclaim this problem -- it is homework. However, I am not asking for the solution, I am wondering if anyone can tell me what I may be doing wrong in solving this specific tension ...
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4answers
1k views

Questions from elevator ride

I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ...
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1answer
148 views

Say we're driving a bike and suddenly hold the brakes?

It's easy for me to imagine that if we brake the front wheel then there is a chance that I'll flip. On the other hand if I brake the back wheel, there is no way it'll happen no matter how fast I ...
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2answers
821 views

When we throw an object in the presence of gravitational attraction is the mass of the object proportional to the time of fall or not?

I was confused when i saw two object of different masses (A and B)falling from the same height(h) but both of them strikes the ground at same time. Is this possible, that masses of the objects are ...
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2answers
3k views

Two objects exert forces on each other, will the reactions affect them?

Two objects go in against each other, and then they collide, will object 1, exerting force 1, necessarily get on it a reaction equal in magnitude and opposite in direction? EDIT:- In my book it only ...
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1answer
531 views

How is a magnetic field translated into physical force?

Related to this question Where do magnets get the energy to repel? If I have a magnet repelling another, eg one in my hand, the other being pushed along the desk, how do the each of the magnet's ...
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4answers
3k views

Gravitational force between two masses

I get it that there will be a gravitational force between objects attracted towards gravity but can there be a gravitational force between two objects resting on horizontal plane? In other words, does ...
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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 ...
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2answers
94 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 ...
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1answer
40 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 ...
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1answer
79 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 ...
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1answer
60 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 ...
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2answers
47 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 ...
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1answer
64 views

Normal force, work and conservativity

I have searched very much on line, both in this site and elsewhere, but found no proof of whether the normal force is conservative or is not, in general. Clearly, if the force is orthogonal to the ...
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1answer
58 views

What is this equation $f^e = f^a - \nabla U$?

Recently in a mechanics class my prof scribbled down something looked like $$f^e = f^a - \nabla U.$$ Where he claimed $f^e$ is the external force on an object, $f^a$ is the applied force on the ...
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1answer
35 views

Integral limits when calculating the work

If I integrate $$dW= \vec{ F} \cdot d\vec{\ell}$$ which are the limits? In $$\int\limits_{W_{inf}}^{W_{sup}}dW= \int\limits_{\vec{\ell}_{1}}^{\vec{\ell}_{2}} \vec{ F} \cdot d\vec{\ell}$$ it is ...
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3answers
133 views

Tension Problem: Finding an angle when only given the tension in two ropes [closed]

A crate is hanging from a rope which is attached to a metal ring through which a second rope runs, as shown to the right. What is the angle $\theta$ if the tension in rope 1 is $1.19$ times the ...
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1answer
68 views

Is the force experienced by a particle influenced by its distance to the focus of the force? [closed]

Is the force experienced by a particle influenced by its distance to the focus of the force?
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2answers
87 views

Fundamental origin of buoyancy force?

Generally, one can think of many different forces in daily life (normal, weight, friction, EM force, buoyancy, etc.). I can think of classifying them fundamentally as in each of the 4 major ...
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3answers
78 views

Newton's Second law of Rotation

In my book (Halliday Resnick Walker) there is a solved example which is as follows There is a uniform disk with mass $M$ = 2.5kg and radius $R$ = 20cm, mounted on a fixed horizontal axle. A block ...
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2answers
201 views

When is tension constant in a rope?

Suppose we have a massless rope with pulling forces applied at each end. In which scenarios is the tension in the rope constant throughout? For example if there is a knot in the rope the tension is ...
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1answer
98 views

What forces cause the centripetal acceleration in circular motion on a merry-go-round?

Suppose you stand on a merry-go-round spinning at $f$ revolutions per second and you are $R$ meters from the center. What forces act on you? If you were tied to a rope like in Fig 2 you would follow ...
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1answer
67 views

How is the load handled between a car and it's wheel?

I know, based on research, that the load of a car is transmitted to the wheels by properly torquing the lug nuts. I'd like to verify this through science. Alas, it's been a decade since I last ...
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1answer
84 views

Why does the water rise upwards when the bottle fall down with accleretion $>>g$?

When a medium-sized bottle filled with water quarterly falls from a height with acceleration $g$, the water remains calm. But when it falls with acceleration $>>g$, the water abruptly rises up ...
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2answers
45 views

Confused about Two Contradictory Facts

When an object hangs from the ceiling, through a rope, the tension force acts upwards, against the force of gravity. However, when a boy pulls a wagon, the tension force acts in the direction he is ...
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2answers
95 views

Why do these two derivations of the formula for impulse contradict?

I was trying to derive $I = F\Delta T$ from $p = mv$. First I converted $v = at$: $$\begin{align} p &= mv \\ p &= m \times at \\ p &= ma \times t \\ p &= Ft \\ \Delta p &= F ...
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2answers
75 views

How to check if a system is in SHM in two spring systems?

I must determine if the system (a) is in SHM. I must arrive to the conclusion that there is a linear restoring force such that $a=-w^2x$. The solution's manual affirms that according to Newton's ...
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2answers
109 views

Is the Fundamental Theorem of Calculus really applicable to the definition of work?

When the force $F$ on an object is not constant, then the work it performs is defined as $$W = \int_{x_0}^{x} F(X)dX.$$ Now, the Fundamental Theorem of Calculus states that $$\text{If}\,\,\, f(x) ...
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votes
1answer
48 views

Maximum velocity on Unbanked roads and why should friction be more than centripetal force? [closed]

Why is maximum velocity on unbanked circular road given by $\sqrt{urg}$ where $u$ is coefficient of friction, $r$ is radius of circular track and $g$ is acceleration due to gravity? Why should ...
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2answers
74 views

How does the force between two charges becomes zero?

In case of Coulombs law, $$ F=k\frac{q_1q_2}{d^2} $$ So, if $F=0$, then $q_1q_2$ must be 0. Is this true?
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1answer
383 views

Force between two blocks on a friction-less surface [closed]

The question is, A single horizontal force $F$ is applied to a block of mass $M_1$ which is in contact with another block of mass $M_2$ as shown in the figure. The surfaces are ...
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votes
1answer
56 views

Friction because of Earth's rotation

Is there some force of friction that acts on bodies due to rotation of Earth. We all know earth is an non inertial frame. If there is some frictional force is there some way to prove it. What i mean ...
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2answers
118 views

Definition of torque for a continuous body

I am working on basic physics definitions. Given a particle at position $r$ (in some coorinate reference system) upon which acts a force $F$, the $torque$ $\tau$ is defined by \begin{equation} ...
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2answers
552 views

Drag force on a flat plate

The solution for this apparently is $\frac{1}{2}C \rho A V^{2}$ where $C$ is the drag coefficient, $A$ is the area and $\rho$ and $V$ are the wind density and velocity. Let's do it without the drag ...
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1answer
45 views

Gravitiation force of a sphere

Was wondering about Shell Theorem, specifically about the immediate results. Force (on a point mass) inside a shell is 0. Force (on a point mass) outside a shell is GmM/r^2 From what i know the ...