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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If I lift a box vertically, why is the work I do equal to the distance I lift it times the force of gravity on the box? [duplicate]

I have problems fully understanding the concept of work, so please forgive me if this is simple. If I take a box of mass $ m $, and lift it a distance $ d $ vertically, why is the work I have done ...
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1answer
178 views

Forces on a helical screw?

The common screws which we use, are right handed helices, the simplest parametric equations of which are:- $$x(s)=\cos(s),y(s)=\sin(s),z(s)=s$$, with $z$-axis as the axis of the helix. My question ...
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1answer
3k views

Does a force do work on an object with constant velocity?

I know that a force does no work on an object if the object's displacement is zero, but if an object is moving at a constant velocity $\bar{v}$, and a force $\bar f$ (let's say that $\bar f$ and $\bar ...
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Homework Question Transformation Energy [closed]

A $1400kg$ car is approaching the hill shown in the figure at $14.0m/s$ when it suddenly runs out of gas. What is the car's speed after coasting down the other side? I think I have to use this ...
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797 views

Punching - Force or Momentum?

If I want to punch a person inflicting maximum damage, what do I need to care about? My force of punching, i.e, do I need more acceleration? Or do I need momentum, i.e my velocity for punching?
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194 views

Power delivered by centripetal force

Does centripetal acceleration deliver power to the revolving object? What I think: Power is given by F.v Since for a body in circular motion velocity and acceleration are at 90 degrees the power ...
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2answers
3k views

Two boxes that are connected pushed by force - what happens between two boxes?

So when two boxes are connected together, and force is applied, two boxes move with the same acceleration. (assuming force is constant.) My question is, how are forces between two boxes get cancelled ...
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1answer
223 views

Free body diagram of rod in sphere

I was finding the free body diagram part of dynamics quite easy until I found this question , Here's how it goes : A rod AB is placed inside a spherical shell, whose inside surface is rough. Draw ...
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3answers
374 views

Do volcano blast changes earth's course?

Volcano blasts are one of the most powerful calamities on earth. When they blast they release large amount of mass in the air just like a jet does. Does such a blast have any effect on the course of ...
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100 views

Conservation of momentum

I've got following problem. There are $N$ particles in an isolated system. The equation of motion for a particle $i$ is ...
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1answer
122 views

Impact Force versus Non-impact force why are they so different?

A mass that has velocity and a force f1, can create a sound and even break a wall upon impact. However if the same force f1 is applied to the wall without any motion (velocity) then the wall will not ...
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1answer
2k views

What force does bathroom scale measure?

When you stand on a bathroom scale, I know that the force displayed is the normal force. Since it is the normal force, then technically the force displayed would actually be Fg= (mass)(acceleration) ...
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3answers
138 views

Exchange particles-real or just mathetical constructs? [duplicate]

Are the intermediate vector bosons real (like the electrons) or just mathetical constructs?i have got a theory to unify the 4 forces, but it does not tell anything about exchange particles in case of ...
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1answer
4k views

Tension in a massless string around a pulley [closed]

A pulley having some mass has a massless string around it, with two unequal masses at the end of the string. Sufficient friction is present between pulley and the string such that the string does not ...
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1answer
113 views

Can Joule's First Law of Thermodynamics be Applied to Atomic Charges?

James Joule established that all forms of energy were basically the same and interchangeable. My question is if thas law is relevant in particle physics. Can a positive charge and a negative charge be ...
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4answers
756 views

How do you tell what forces do no work?

The total mass of the children and the toboggan is 66 kg. The force the parent exerts is 58 N (18 degrees above the horizontal). What 3 forces/ components do no work on the toboggan? I said the ...
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2answers
12k views

Calculating force of impact

Since $\text{force = mass}\times\text{acceleration}$, is it right to say that an object traveling at a high constant velocity (zero acceleration), exerts zero force upon impact with a stationary ...
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1answer
93 views

Do all forces act in the same way where gravity is close to zero?

Suppose that I put in the outer space (where gravity from other bodies is negligible) a large, perfectly round sphere totally filled with water. At the bottom (even though "bottom" doesn't make much ...
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3answers
511 views

Lagrange-Euler equations for a bead moving on a ring

A bead with mass $m$ is free to glide on a ring that rotates about an axis with constant angular velocity. Form the Lagrange-Euler equations for the movement of the bead. Solution: Let us ...
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1answer
182 views

What is the significance of Planck force?

I have been curious to find what could be the significance of Planck force? It is calculated by the formula $c^4/G$, where $c$ is the speed of light; $G$ is the gravitational constant. Thus (the speed ...
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1answer
454 views

Mechanics Question: Work and Power

I'm a pure mathematician by trade, but have been teaching myself classical mechanics. I've got to the chapter on Work, Energy and Power and I've found an example that is causing me some problems. ...
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1answer
145 views

Nothing escapes BHs, gravitons mediate gravity, so why do BHs gravitate? [duplicate]

Possible Duplicate: How does gravity escape a black hole? Nothing escapes black holes, gravitons mediate gravity, so why do black holes gravitate? My question is, "where is the hole (no ...
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3answers
310 views

Doubts with levers

I'm studying for a test of static rigid body and I'm having doubts on how to solve problems involving levers with weight. If I have, for example, a lever 10 kilograms and 3 meters long and one support ...
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1answer
884 views

Trying to understand the tension in a spring with two weights attached [duplicate]

Possible Duplicate: Why I think tension should be twice the force in a tug of war For (A) in this image, I would think the tension should be should be 2mg. However, my book says the ...
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1answer
731 views

Can I use Newton's second law to solve what seems to be a torque problem?

The Problem: An 8-m-long beam, weighing 14,700 N, is hinged to a wall and supported by a light rope that is attached 2.0 m from the free end of the beam. If the beam is supported at an angle ...
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1answer
504 views

Mass points of a Mass-spring model

Let's say I have a mass spring model like the one in the picture below: So, there are 3 parts of the spring joined together in an equilateral triangular manner. Each of the joints has a mass of ...
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1answer
582 views

A Lawnmower Problem

For my physics class we were just given an exam that asked the following: A 12Kg lawnmower is pushed with a constant force along the 30* handle with 80N. Break the Forces into its vector ...
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1answer
338 views

Question about finding $k$ in Hooke's Law

My textbook (Advanced Engineering Mathematics by Dennis Zill) offers the following explanation of Hooke's Law: By Hooke's Law, the spring itself exerts a restoring force $F$ opposite to the ...
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1answer
209 views

Rotating sphere and circular trajectory: minimum speed

I have a sphere (mass = 3 kg), constrained to a fixed length rope, rotating (radius = 5 m) on a vertical plane. My textbook ask me about the minimum speed in the highest point in order to keep the ...
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2answers
475 views

Hanging a Hammock

I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end. How would I determine how heavy the cement needs to be so that it would ...
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1answer
106 views

In hydrostatics, is it possible for the bouancy to be greater than the weight of a body?

In the diagram we have two bodies, with density and volume $\delta$ and $V$, and a fluid $\ell$. $$\delta_1=0,7 \rm\frac{gr}{cm^3}$$ $$\delta_2=2 \rm\frac{gr}{cm^3}$$ $$V_1=100 \rm {cm^3}$$ $$V_2=10 ...
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1answer
277 views

Does friction act in the same way in different directions?

A physics textbook is launched up a rough incline with a kinetic energy of $X$ joules. When the book comes momentarily to rest near the top of the incline, it has only gained ($X-20$) joules of ...
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1answer
265 views

Momentum question?

The problem: In a car crash, a passenger with a mass of 82kg is not wearing a seatbelt. The car is travelling at 45km per hour. What impulse must the car's airbag provide in order to stop the ...
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1answer
803 views

Does the earth's gravity affect horizontal movement?

In a frictionless environment, would the weight of an object affect how hard it is to move it horizontally? Since without friction, there is no horizontal force resisting your applied force, would the ...
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727 views

Question involving Vectors and Forces

This is a question I found in Mechanics for Engineers by Beer & Johnston. A 600-lb crate is supported by the rope and pulley arrangement as shown below. Write a computer program which can be ...
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1answer
494 views

Laws of Motion: Acceleration to be applied on a free falling object to reduce velocity to 0

Assume that an object of mass 'm' is falling to the earth.The force acting on the same would be F = m*g = 10m (assuming g = 10m/s^2). In this case the velocity of the object at time 't' = 10 seconds ...
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What is the force exerted on a body that doesn't move?

If I push against a brick wall I'm exerting a force against the brick wall the the brick wall will exert the same force against me. These will cancel each other out and neither myself or the wall will ...
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2answers
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Calculate the weight a simple plank can support [closed]

I'd like to build a simple desk; just a single plank of wood (or a few side-by-side) with solid supports on each end of the desk. What I'm trying to figure out is how thick a plank I want to use for ...
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1answer
397 views

if a force is 1 newton metre, what is it at 2 meters?

If I have a force, say 24 kg/cm what would that equate to at 2cm? I would like to know the formulae for calculating this. For example. If a motor can hold an object of 24kg at 1cm from its pivot ...
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1answer
45 views

Understanding the relationship between electric energy and force

I'm trying to do the following problem: One of the three types of radioactive decay is "β decay", during which protons decay into neutrons or vice­versa, emitting either electrons (β­) or positrons ...
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2answers
14 views

If two bodies move opposite to each other when brought in contact, what is the direction of force of friction?

We know that when a body is at rest and other is dragged over it then a force is produced which opposes the motion and consequently its direction is negative to the force applied on body to produce ...
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2answers
47 views

Calculation of a normal force with an angle

I'm currently studying forces in physics and in this example, it states that Fn +Fay = mg. Why is this so? Is it because they are both in the same direction?
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1answer
17 views

Force of tension on both sides of one string- 2 questions

Here's something I want to ask you guys about: Many times downward N1 and N2 are ignored in exercises. Why? If forces of tension are balanced by each other, why won't objects just fall? Cheers ...
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1answer
22 views

What happens when a high speed motor tries to drive a heavy car? High torque?

I'm trying to figure out what would happen if a really high speed motor - which has enough power to drive a car, but very high RPM & very low torque - tries to move a car. Does it get stuck ...
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1answer
19 views

What forces act on an object submerged in flowing fluid in an enclosed environment (i.e pipe)?

Let's say we have a pipe with water flowing through it and obstacle is inserted into the pipe and is rigidly fixed to the inner wall so that it does not get washed away. What forces are exerted by ...
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2answers
48 views

Direction of friction vector when acceleration is zero

There is a box on a ramp, there is Wx that makes it fall, Tension that pulls it up the ramp (a rope) and Friction. The thing is, how can I determine the direction of the friction? For me, friction ...
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1answer
45 views

How the torque/moment-of-force can be mathematically defined?

Given the definition of torque/moment-of-force $\mathbf F$ applied in $P$ with respect to the pole $O$ $$ \mathbf M_O=\vec{OP}\times\mathbf F $$ and given that the vectors $\vec{OP}$ and $\mathbf F$ ...
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4answers
86 views

Find the work done in moving an object along a vector r with a force F [closed]

$$r=3i+5j-2k$$ $$F=3i-3j+2k$$ What do I do. I know that work = force x distance. However, what vector operation should I do? I was wondering whether I should possible find the unit vector of r and ...
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1answer
38 views

Find angular velocity of motor

I'm quite bad at this, but I'm trying to change that and I need some assistance. Please bare with me while I attempt to explain what I'm trying to figure out and correct me where I'm wrong. Basically ...
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2answers
36 views

Different sized pneumatic Pistons [closed]

If two different sized pneumatic pistons have the same amount of air pressure, will they exert the same amount of force? If not, would a bigger or smaller piston have more force? And an explanation ...