All Questions
Tagged with newtonian-mechanics work
1,269
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Confusion regarding Newton's Third Law and Conservation of Energy
A specialized system consisting of two bodies A and B. A has 1 J of energy and can thus displace B 1 m by applying a force of 1 N. But at the same time, A also experiences a reaction force and is ...
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1
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Why is the direction of friction not being considered in this problem for calculating the work done?
The solution to the problem happens to be $mg(h+kl)$ because the work done by force $F$ has to be equal to the sum of the work done by friction and gravitational force. But how is the work done by ...
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4
answers
150
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Is Energy stored work? [closed]
Energy is the ability to do work therefore Energy should be the primitive form of work. But I cant find any conformation, if wrong can anyone explain to me the relationships between Work, energy, and ...
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6
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Can there be acceleration without work?
Since $W=Fs$, $F=\frac{W}{s}$. When you substitute this in the formula for acceleration, $a=\frac{F}{m}$, you will get that $a=\frac{W}{ms}$. Then, when work equals zero, acceleration will be zero.
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2
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Is Energy stored Force?
I am currently studying the relationships between energy work and force. I am trying to conceptualize them into one concept of causality. When a force is applied work is done, and energy is ...
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1
answer
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Work done on a body and work done by the body
I want to know that, if we suppose that, if a ball is falling freely then work would be done on the ball by gravity so energy would be given to the ball? and when the ball rebounds after striking the ...
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2
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Proof Of Conservation Of Energy
Yesterday I was trying to prove The law of conservation of energy, But in a different approach:
Using the concept of vector field here is how it went:
I assumed a force field $\mathbf{F}=f(x,y,z){\...
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1
answer
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Does Accelerating to Double the Speed Require Quadruple the Fuel Consumption, or Double the Fuel Consumption?
I'm writing a piece on the efficiency of trains versus trucks, and one of the points I was making is that trains can take advantage of not having to stop and start multiple times. This is obviously ...
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1
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Is a velocity-dependent force $\vec{F}$ that doesn't do any work on an object a conservative force? [duplicate]
Let's consider a point like object with mass $m$ upon which acts a force $\vec{F} = \vec{c} \times \vec{v}$ ($\vec{c}$ is supposed to be a constant vector). Given that $\vec{F}$ is perpendicular to $\...
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0
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Aren't the virtual work/virtual power principles in mechanics simply solving for the vector differential equation of motion in a preferred direction?
My conceptual understanding of the virtual work/virtual power principles is that, by hypothesizing "virtual displacements"/"virtual velocities", one can solve the equations of ...
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6
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How can a system have kinetic energy if the centre of mass of the system is stationary?
(I'm doing high school physics so please go easy with the crazy calculus)
From what I understand, a system has translational kinetic energy if the system of mass is moving at a velocity but the ...
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A man is rowing a boat upstream is at rest with respect to shore is he doing any work
Is the man doing any work or not when is rowing a boat upstream? I m confused That Okay he's at rest with respect to Shore but at some sites it can be seen that Yes he is doing work then how he is ...
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Motivation for definition of work [closed]
Why do we take the dot product in the work energy theorem? Consider the integral
$$\int\vert\vec F\vert\vert d\vec r\vert$$
Why don't we define this to be work done for example, instead of $\int\vec F\...
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1
answer
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How much more fuel to double the speed?
Suppose it requires a certain amount of fuel to accelerate a car (or a spaceship) from 0 to a speed $v_1$ (in some initial frame of reference). Let's ignore all friction forces, and only consider ...
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Is the topic of gravitational potential energy convoluted and unnecesary? [closed]
If we throw an object upwards from the surface of the Earth, we do some work on it to give it kinetic energy. Now as it travels up, Gravity of the Earth does negative work on it till it loses all the ...
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How is work done by Tension zero in this case?
How is the work done by tension zero in this case. There is no horizontal force acting so the centre of mass won't displace in the horizontal direction as it will be in vertical.
But the work done by ...
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2
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How can we jump when the ground does no work on us? [duplicate]
This may seem like a silly question, but how can we jump when the ground does no work on us?
When we jump off the ground, the ground does not move. This means the force from the ground on us does zero ...
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3
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Why energy of a system equals to sum of its mechanical energy and its internal energy? [closed]
My books said that energy is a quantity that:
Its variation equals to work done on system (1)
It equals to sum of its mechanical energy and its internal energy (2)
So, can (2) be inferred from (1)?
...
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1
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What should I take as virtual displacement?
A bicycle rider has M. The wheels of the bicycle are at distance l apart and horizontal distance between the seat and the rear wheel is d. Use principle of virtual work to find the normal reactions on ...
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How can the Joule be the unit of both work and energy?
Say a person applies 1 N to a box with a mass of 1 kg, displacing 1 m. This is one Joule of work
(1 N for 1 m).
Now say the person applies 1 N to a box with double the mass, displacing 1 m as well. ...
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7
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Work-energy theorem and Newton's second law
I was going through a book in which it was written that
'Work-energy theorem for variable force, in general, does not incorporate the complete dynamics of Newton's 2nd law of motion as the theorem ...
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1
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Distance a block slides along a surface with friction given with an initial velocity [closed]
For this part (e) of this problem,
Source: https://ocw.mit.edu/courses/8-01sc-...647ea989a352a972dc4b3dfe_MIT8_01F16_pset7.pdf
The solutions are,
However, I don't understand why they only used a ...
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Why is force "accumulated" more at a higher speed?
I tried to understand why kinetic energy is proportional to the square of velocity. In this endeavor I stumbled upon a book "Emilie du Chatelet: Daring Genius of the Enlightenment" (ISBN 978-...
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2
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291
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What is energy and how it is classfied?
My physics book defines energy like this:
"Everything that works has energy, energy $E$ of a system is a function of state and its variation $\Delta E = W$ ($W$ is work done on system)".
...
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Work-Energy Theorem and First Law of Thermodynamics [duplicate]
I am little confused about the connection between these two concepts in Physics:
First, in classical mechanics, a basic result is the work-energy theorem, which states $$\Delta T = -W.$$ This equation ...
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1
answer
51
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How to derive equation for thermal energy ($E$ thermal = Friction force X Distance)
We are covering the energy principle in my physics course and so far we have been using the equation $$\Delta KE + \Delta E_{th} = W_{Ext}$$ which is change in kinetic energy plus change in thermal ...
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Equilibrium and maximum velocity position of a person jumping on pogo stick (spring)?
Consider the following diagram:
It is given that:
A is the position of maximum compression of spring and the child is at rest(at that instant).
At B, the child is having an upward velocity and the ...
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2
answers
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Work done by ladder on the boy and work done by boy on ladder [closed]
I was stuck in a question:
In a children's park there is a slide which has a total length of $10 \,\mathrm m$ and a height of $8 \,\mathrm m$. Vertical ladder is provided to reach the top. A boy ...
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4
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Work done by vertical force
We know that work is defined by the dot product of force and displacement,which mathematically means $W=Fs\cos \theta$ in scaler. But let's suppose an object is moving in $x$ axis. It's vertical ...
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3
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Work done by the force of gravity
My question is very similiar to this one: Work done by gravity on falling object does not seem to equal change in mechanical energy
As I've understood it, work is only done on an object if the object ...
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4
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Does a moving object with a constant velocity do any work?
Since Work=Force$\cdot$ Distance and the net force on a moving body is zero, does that mean that no work is done by a body moving with a constant speed?
Also, the work done is the energy expended. If ...
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Importance of keeping constant velocity
In finding work done by a spring or gravity (i.e conservative forces), when an external agent does work, why is it done so that velocity i.e kinetic energy remains constant? I know from Work energy ...
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What is the derivative of potential energy with respect to $x$? [duplicate]
I was reading an article which was proving the conservation of energy with calculus, but they did not explain why the derivative of potential energy with respect to $x$ is the negative force.
$${dU\...
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When is the work done minimum?
Work $W$ is defined as the dot product of the vectors force $F$ and displacement $s$.
The dot product can be written as the products of the magnitude of the force, magnitude of the displacement and ...
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Work done and deriving elastic collisions
Using Newton's second law, it is possible to write the work done on a path going from position A to B as:
$$W_{AB}=\int^B_Am\frac{d\vec{v}}{dt}\cdot d\vec{r} =m\int^B_A(\frac{d\vec{v}}{dt}\cdot \vec{v}...
user332426
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Find the speed of the particle when it has covered a displacement of magnitude $L$ [closed]
This is my first question on this site.
A particle of mass $m$ is constrained to move along $x-\textrm{axis}$. The only force acting on the particle is given by $$F=F_0\cos\left(2\pi\frac{x}{\lambda}\...
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Work power energy related question [closed]
If work done by conservative force = $-\Delta U$ always (even if there is air friction), and Work-energy theorem is applicable anywhere,
and we derive law of conservation of mechanical energy using ...
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1
answer
41
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Change of velocity without doing work
Body of mass $1\rm\, kg$ is moving towards left side at velocity of $-2\rm\,m/s$ and is slowing down due to the constant external force until it stops. After that, it's speeding up towards the right ...
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2
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Why does small work done mean $dw=f.ds$ and why not $dw=df.ds$ and why not $dw=s.df$? [duplicate]
Work, power and energy questions.
Why does small work done mean:
$$dw=f.ds$$
and why not:
$$dw=df.ds$$
and why not:
$$dw=s.df \ \ ?$$
2
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2
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Work Integral and its derivation
The work integral is something I saw long time ago and in completely understood it.
\begin{align}
W_{12} & =\int F(x)dx=m\int^{t_2}_{t_1}adx=m\int\left(\frac{dv}{dt}\right)dx=m\int\left(\frac{dv}{...
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Help me understand the derivation of the kinetic energy formula please
In my physics textbook, kinetic energy is defined as $W$Net $=$ $\int m\frac {dv}{dt}$ $dx$ This makes sense to me just fine. The book goes on to rearrange the integral to say the following:
$W$Net $=...
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4
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Confusion regarding work done by external force
Suppose a ball from outer space is moving towards earth. The force of gravity attracts the ball more and more strongly as it moves closer and closer to the earth. Now, let me apply an external force ...
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2
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Orientation of gravity force in energy [closed]
My apologies in advance if this is a stupid question.
A 0.20 kg rocket in a fireworks display is launched from rest and follows an erratic flight path
to reach the point P, which is 29 meters above ...
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Relationship between work and potential energy
Ultimately what I am trying to do here is convince myself that the following relationship holds:
$$F = -\frac{dU}{dx}$$
for a force $F$ and a potential function $U$. We have that the work $W$ can be ...
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1
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What happens if I rewrite the acceleration in work formula this way?
Work is known as
\begin{equation}
W=\vec{F}.\vec{q},
\end{equation}
thus for a gravitational force $\vec{F}_g=m\vec{g}$ we have
\begin{equation}
W=mgh.
\end{equation}
My derivation is as follows:
\...
user330731
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How to prove that work due to conservative forces are independent of path?
The Wikipedia article on conservative forces says,
A force field F, defined everywhere in space (or within a simply-connected volume of space), is called a conservative force or conservative vector ...
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What is the work done in lifting the bucket? [closed]
A bucket is tied to a well with a chain 20 meters long to lift water. If the weight of the chain is 2 kg per meter and the weight of the bucket filled with water is 20 kg, what is the work done in ...
1
vote
1
answer
87
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Virtual work method in pulley [closed]
The problem illustrates two pulleys whose two ends are going downward with velocity $v$. The problem was about finding the velocity of the point $X$ i.e the point where the strings of the two pulleys ...
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3
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Does gravitational potential energy exist?
If an object is taken at a height $h$ above the ground, its potential energy is $mgh$. When it is then released from there, it falls freely due to the force of gravity and its kinetic energy increases....
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1
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Work done on person standing on an escalator
Say a person stands on the escalator which is going downwards. The normal force by the escalator does negative work, and the gravity does positive work. The person apparently loses some potential ...
