What is Work done: Definition and 1000 Discussions
In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, it is often represented as the product of force and displacement. A force is said to do positive work if (when applied) it has a component in the direction of the displacement of the point of application. A force does negative work if it has a component opposite to the direction of the displacement at the point of application of the force.
For example, when a ball is held above the ground and then dropped, the work done by the gravitational force on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to the ground (a displacement). When the force F is constant and the angle between the force and the displacement s is θ, then the work done is given by:
W
=
F
s
cos
θ
{\displaystyle W=Fs\cos {\theta }}
Work is a scalar quantity, so it has only magnitude and no direction. Work transfers energy from one place to another, or one form to another. The SI unit of work is the joule (J), the same unit as for energy.
The answer is as such: There’s only one way for the system to move: the rectangle can deform into a parallelogramso that the left horizontal arm moves up, and the right horizontal arm moves down by thesame amount. Then the total virtual work done on the scale by the weights is zero, so thesystem...
Since we want the current to stay constant, the change in potential energy that's caused by the coil flipping in the magnetic field should be "undone" by the work done by the power supply, so shouldn't ##W = -\Delta U## ? the answer guide did it without the negative sign, so I'm wondering if the...
For part a and b, I can't see a clear path to finding the answers. In order to find the x component of the applied force I need to know the friction. In order to find the friction I need to find the y component of the applied force, but I can't think of a way to find either.
I thought of...
It is clear that the process is isothermal else it is not possible to find heat absorbed.
$$W=-P_{ext}(\Delta V)$$
However ##P_{ext}## is not given. How do I proceed?
I tried taking ##W=-(P_2V_2-P_1V_1+P_3V_3-P_2V_2)=\Delta(PV)## but it is wrong for obvious reasons.
I was researching about conservative and non-conservative forces, and there is some information in a website that sates that the work done is independent of path if the infinitesimal work 𝐹⃗ ⋅𝑑𝑟⃗ is an exact differential. It further states that in 2 dimensions the condition for 𝐹⃗ ⋅𝑑𝑟⃗ = Fxdx...
The question was this:
My calculations show that the answer should be equal to work done on crate to make it reach the same velocity which is equal to 216 J but the answer given is 432 J
It is believed that extra energy is needed to overcome friction but friction is an internal force and...
My question is whether I've formed the integral for the work done correctly? It just seems a bit unwieldy to me...
If I call the extension of the spring ## x ##, I can see that ## z = \frac l 2 + x ## and ## z^2 = \left( \frac {l} {2} \right)^2 + y^2 ##. Combining them gives: $$ x = \sqrt {y^2...
This question states that the normal force of the stairs on the woman does NO work. I do not understand how this can be. I would reason like this:
The woman propels herself up the stairs using her legs. Her legs push down against the stairs, and the consequent normal force pushes upwards on her...
The mass of the bike and person is 190kg
Calculate the average accelerating force from X to Y, if the bike has a velocity of 30 at point Y.
I am struggling with this question, I know that Fx = Work Done, but I also know that the only way to release GPE as KE is for gravity to do positive work on...
Shouldn't work be minus when the man climbing up and force on him is down?
shouldn't the power be also in minus?
Can someone explain to me why is it positive please!
Here is the question, I am struggling with it as in all the past questions I have done it didnt matter if you worked out the work done by each force and then added it all together or if you added the forces together and then worked out the work done by the total force, but here the net force is...
I think that the work is meant to be work done for instance in power stations. Or is it similar to work I do on a body when I lift it for example? But how can we then do that work on our Earth? I just need to understand the task, otherwise I want to solve it myself.
The problem involves...
The answer is (D), but I don't understand why.
Option (A) is wrong because the work done = 0. Then, I divide the motion into 3 parts:
1) motion on snowy surface
Since the sledge is being pulled horizontally (let assume to the right), there will be tension force T to the right and friction...
For this problem,
dose anybody please give me guidance how they got 74 K as the answer? Note that chat GPT dose not give the correct answer (it gives the temperature of the gas is 1500 K).
Many Thanks!
For this derivation,
I am not sure why the bit highlighted in orange is not positive since the displacement of the piston is downwards in the same direction as the force applied.
Many thanks!
We want to figure out how much work friction does on a block as it slides down an inclined plane with a rough surface.
we find the force due to gravity that pulls the block down the ramp, that's found by M * g * sin(θ),
The normal force on the block is given by M * g * cos(θ).
The force of...
For example, if a ball is from a certain height, the work done is 0 as there is no change in total energy the Ef =Ei. However, there is a constant force applied over a certain distance, suggesting work is being done. Which aspect am I forgetting/missing? Or is it that the definition of work done...
For this problem,
The answer is ##-4.70 kJ##. I am not sure what I am doing wrong.
My working is
## W = mgr\cos\theta ##
## W = mgr\cos150 ## (since angle between ##\vec g## and ##\vec r## is 150 degrees)
## W = -mgr\frac {\sqrt{3}}{2} ##
## W = -mgr\frac {\sqrt{3}}{2} ##
## W =...
Consider a merry-go-round (carousel) with a tube fixed radially on it. I use a pole to push a bowling ball slowly through the tube towards the center. (Slowly, so that the kinetic energy is negligible when the ball reaches the center. Also assume zero friction).
What happens to the work that I...
I have found the work done for 100 N, 70 N and 30 N force, but I don't know how to find work for 100 N force that is acting downwards.
Force 70N:
W=F×d = 70 ×0=0 Nm (Force is perpendicular to the distance moved)
100 N force:
W=F×d=100×0.5=50 Nm
30N force:
30×-.5= -15Nm.
Please check whether...
(picture of diagram below)So the task goes like this: gas is ideal. Process 3->1 s adiabatic and in process 1->2 work done is 1200J. Fill the table.
I don't know how to calculate work done in an adiabatic process because p2 and V2 are not given and I don't know gama(Cp/Cv).
I know that deltaU...
Hello,
Suppose I have a spherical hole in a elastic infinite space. I apply a time-dependent pressure to the inner surface of the spherical hole.
I know p = f(t).
If I only consider this as an elastic problem, no failure happened, how can I calculate the work done by p during the time from 0...
I am post-processing a simulation.
A spherical is meshed by many little triangles. A time-dependent pressure (p=10*t) is equally applied to the inner surface of a spherical in the normal direction all the time. After t1=0.1s, the spherical is broken, and each little triangle is disconnected...
I'm wondering what's the difference between work done on quasi-static and non quasi-static expansion.
In a quasi-static process, the gas inside the system must do a work to "extend".
However, in a non quasi-static process, where the gas inside the system doesn't move fast enough to "push" the...
Hello
The formula Mgh is commonly accepted as the work done by raising a mass by a distance h, where M is defined as the mass of the object raised.
However, is this really the mass, or the weight, simply obtained by weighing the object? If it's the weight, then doesn't the equation...
Hi! So, I've actually already solved this problem.. for the most part.
I have split up the work into two sections, floor 0 to 10, and floor 10 to 15.
From floor 0 to 10, I did
## F_{elevator} = w_{pass.} + w_{elev.} ##
## F = (70)(20 (num. of pass.))(9.8) + (800)(9.8) ##
## F_{elev.} = 21560N...
I don't understand what I have done wrong in part (c) I have the initial velocity for the second part of the motion and have the final velocity zero and then the net work done is W_mg + W_Fs and the actual answer for x is 2.37m
Could I get some help/tips please, thanks in advance.
Here is my...
During a thermodynamic cycle, an ideal thermal machine absorbs heat Q2 > 0 from a hot source and uses it to perform Work W > 0, giving a cold source a heat Q1 < 0 with an efficiency of 20% . How much is the work done as a function of Q1 ?I have 2 question regarding this problem: 1) Why is Q1 the...
This is a thermodynamics question. A gas absorbs 10 000 J of heat , it releases 3000 J and does 2000 J of work. How much has the internal energy varied?
So I did 10 000 - 3000 -2000 = 5000 J so internal energy decreases by 5000 J. But the correct answer is A) it increased by 5000 J . How ?
The equation I know for adiabatic work is W = P1V1((V1/V2)ϒ-1 - 1))/ϒ-1, but this involves ϒ, but I can use ϒ = Cp/Cv = Cv+R/Cv = 1 + Cv/R, does this seem correct? But I still have a P1
I will summarize briefly my reasoning for both letters, since the answer is immediately after that:
A) The work is quasi-static, and the pressure is approximatelly constant and equal to the atmospheric pressure, so the works is $$W = -p\int dV = -p_{0} (V_{0}-V)$$
B) The work is fast, fast...
The reason I'm posting this is because I'm confused about the reasoning behind the equation. For oppositely charged particles, wouldn't work done increase with distance? According to this equation you get a higher magnitude of work done the smaller the distance. How can that be? I got the answer...
##W=mgh=100(\sin 37)2=-120J## Right answer!
But the question is asking work done by the person. So again I wrote two eqns
##F_N\sin 53+F_D\sin 37-100=10.2a_y##
##F_N\cos 53-F_D\cos 37=-10.2a_x##
I just need ##a_x## and ##a_y## to solve.
So for the work done by the kinetic friction, the displacement along the incline is ##s## as given.
What I canNOT understand is why the displacement in the y-direction is used for the work done by gravity i.e. ##W = -mgh## where ##h## is the displacement in het y-direction. This instead of the...
Hello guys, I was wondering if someone could provide me some help on this problem.
for (c), I know that it will be 0 as the amount of word done from A to B = the am of work done from B to C.
But, What I receive as seen in the picture is 2.11N Which is not correct..
In the first try I used a...
The answer key is zero because the areas are above and below x-axis and have equal magnitude so canceling out each other.
But I am confused about the solution
Area 1 is above x-axis but I think the work done is negative since the sign of ##F## and ##x## is opposite. Work done on area 2 is...
Hello,
I'm getting a little confused and would appreciate some clarification.
If a weight lifter lifts a weight of 2500N a distance of 2m, the work done by the weight lifter's force on the weight is 5000J. The work done by the weight force due to gravity is -5000J. The weight lifter then...
##\Delta K=K_f-K_i=W_a+W_g##.(##W_a##, work done by applied force and ##W_g##, work done by gravity) In case of uniform motion with velocity u, kinetic energy is equal. Change is zero. ##W_a=-W_g## If one force transfers energy into the system then the other takes out of the system. Energy of...
I encountered a problem regarding the appropriate sign needed to be taken for the work done on a dipole when it rotates in a uniform electric field and would appreciate some help.
The torque on a dipole can be defined as
τ=PEsinθ
The work done on a dipole to move it from an angle ##\theta_0##...
A gas with a volume of 8m^3 with a temperature of 400K gets warmed up to 550K with a constant pressure of 200Kpa. How much work has the gas done to the environment?
I think i might need to use the ideal gas law for this which is:
( P * V / T = N * K ) Where V is volume, T is temperature and N...
The answer key is (b) but in my opinion it should be (d) because I think about work done by friction on wheel of car when the car moves. Let say the car moves to the right, then the wheel will rotate clockwise and the direction of friction acting on the wheel by the road will be to the right and...
Let me start out by saying it's been a LONG time since I've touched any thermodynamics but I'm starting to think that the answer for all 3 parts are the exact same (at least for work)
Namely
##W = \int_{\frac{L^3}{2}}^{L^3} P(V) \, dV = NkT_0 \int_{\frac{L^3}{2}}^{L^3} \frac{1}{V} \, dV =...
Here's where I got the questions:
These are from a worksheet I downloaded online: Answer Key
The answer key says that the answer to the first question is 500J and for the next question it's 433J.
It says constant speed though, so I don't understand why the answers aren't zero. I get how they...
This is my solution ,and I just use the definition .But I still feel unclear about the concept of non-conservative force.$$ W = F x = 30N (\frac{1}{2}\pi r ) = 56.2 J $$
$$ E_{system} = \Delta K + \Delta U = W $$
$$ (K_{f}- K(i))+(U(f)-U(i)) = W $$
$$ (\frac{1}{2} *m{V_{f}}^2...