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.
Homework Statement
A standard man climbs 15 m up a vertical rope. How much energy (in cal) is dissipated as heat in a single climb if 23% of the total energy required is used to do the work? (Assume the standard man has a mass of 70 kg.)
Homework Equations
Q = mgΔh
The Attempt at a Solution
I...
I am confused how a charge could have negative work done.
To clarify, I was doing a problem earlier in which a positive charge and negative charge are moving towards each other. I used the equation
work = Δv * q
And when I was doing this, the change in electric potential, Δv, was negative, and...
Please see attached sketch. I am trying to determine the total work done by this system. I am not sire where to even start. I know w=fd, but i am not certain how that applies to a rotating object. Please advise.
If an object with 1kg mass falls free (no air drag), from 100 meters high, and the gravitational acceleration is 9.81, then the mechanical energy will be: 1*9.81*100 = 981 joules.
The work the gravitational force does on the object will be: 9.81N*100m = 981 joules.
Another object with same...
Assume a person is at space, and assume there's no friction or gravitational force in that space.
The person has a bow and arrow. He stretches the arrow on the bow, and then shots the arrow out in the space. Since there are no friction and gravitational force in that space, the arrow will have...
Homework Statement
A sample of 1.60 mol H2 (Cv = 20.5 J K-1 mol-1) at 21°C and 1.50 atm undergoes a reversible adiabatic compression until the final pressure is 4.50 atm. Calculate the final volume of the gas sample and the work associated with this process. Assume that the gas behaves ideally...
When we calculate the work done by a force applied on an object (suppose force and movement are in the same direction and a constant force) do we take into account the relative distance ot the absolute distance.
When saying relative distance i mean if the object is moving on top of a platform...
Here is problem I quickly made up:
Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N.
Here's the confusion:
By using the non-conservative force work energy...
Homework Statement
How much work per step per leg in the race? How much work must he (single leg) squat to equate 1 step of work in the race?
The given variables are:
Displacement: 100 meters
Time: 9.65 seconds
runners weight in kg= ?
100 steps to complete 100m race, alternating legs...
Homework Statement
[/B]
In gravity-free interstellar space, a spaceship fires its engines to speed up. The total thrust of the engines as a function of position is shown in the graph below. F on the graph represents 79 kN of thrust. The rocket's mass is 11500 kg. Note the units on the graph -...
Homework Statement
[/B]
A force acts on an object along an x axis. The force varies with position as shown in the graph below. On the graph, F = 52.0 N. Find the work done by the force as it moves the object from x = 0 to x = 15.0 m.
Homework Equations
[/B]The Attempt at a Solution
So what...
Homework Statement
I need to solve the following D.E for ##\phi(x,t)##
$$[\frac{\partial}{\partial t} - D \frac{\partial ^2}{\partial x^2}]\phi (x,t) = f(x,t)$$
with the help of the following DE with a Green's function
$$[\frac{\partial}{\partial t} - D \frac{\partial ^2}{\partial x^2}]G...
Homework Statement
Let ##G## be a non-directed graph with non negative weights. Prove that the multiplicity of the eigenvalue ##0## of ##L_s## is the same as the number of convex components ##A_1,\dots, A_k## of the graph. And the subspace associated to the eigenvalue ##0## is generated by the...
Homework Statement
A grocery cart with mass of 19.3 kg is pushed at constant speed along an aisle by a shopper who exerts a force of 13.1 N on the cart at an angle of 18.3 from the horizontal. The aisle is 15.1 m long. The coefficient of friction is 0.0658.
Find the work done on the cart by...
Hello, I want to make a Slayer Exciter circuit with a Tesla Coil. I have my parts laid out, but I want to make sure that they would work before purchasing them.
Off and On switch
I have one
0.5'' PVC pipe
I assume any would work
9v Battery
I own one
9v Battery holder
I own one
22k ohms...
Hi guys.
I want to make a question about what kind of job can a physicist do.
Excluding the academic carrier and the research, which kind of job can a physicist do?
It is true that there are physicist that work at Wall Street?
If yes, what kind of job they do there?
A technical job?
I don't...
Homework Statement
A spiral staircase in a building is in the shape of a helix of radius 5 meters. Between two floors of the building, the stairs make one full revolution and climb by 4 meters. A person carries a bag of grocers up two floors. The combined mass of the persona and groceries is 70...
Too many on the market, too many promises. Is there certain chemicals that I should look for when I'm shopping for pet odor removal products?
Move okay. (Chemistry? General?)
Homework Statement
Homework Equations
W = ΔKE
W = KEf-KEi
The Attempt at a Solution
W = .5mvf2 -.5mvi2
I know that final KE for A is 4 times the KE of B because for A ... KEf = 1/2 m (2v)^2
4KE = 1/2 m v ^2 for A
I don't know what initial KE for both of them are... so how do i know if that...
Hello,
Consider two equal masses moving away from each other at the same speed. The total momentum of the system is zero, so the total momentum of the system is zero. Therefore, the centre of mass has no speed.
The total energy in the system is ##mv^2##, due to the kinetic energy of the two...
These two things seem to be exactly the same (even down to the same formula), so I'm having difficulty understanding why they are two different terms.
Is circulation just the work done as you go around a circle once?
Homework Statement
Estimate the pressure increase required to impart 1 J of mechanical work in reversibly compressing 1 mol of silver at room temperature. What pressure rise would be required to impart 1 J of work to 1 mol of alumina at room temperature? For alumina take the molar volume to be...
Homework Statement
Calculate q, w, ∆E, and ∆H for the process in which 93.0 g of nitrous oxide gas (N2O) is cooled from 179°C to 55°C at a constant pressure of 4.00 atm.
Cp(N2O) = 38.70 J K-1 mol-1
Homework Equations
q= mCΔT
ΔH=n(Cp)=n(qv)ΔT
ΔE=q+w
w= -pΔV
*Probably something else too but I'm...
Homework Statement
What is the minimum work needed to push a 1000-kg car 300 m up a 17.5 degree incline?
A. Ignore friction
B. Assume the coefficient of friction is 0.25
Homework Equations
W = F*d
Net force = ma
The Attempt at a Solution
At first I did:
Work = F*300*cos17.6
but I later...
Greetings all,
I am an undergrad working on my first first-author paper in theoretical / computational condensed matter physics (near the computational materials science end of the spectrum) and I am looking to getting it published. My advisor has published in many journals, from mid to high...
I have the problem below.
I know that net work is equal to the change in kinetic energy which is Wnet= 0.5mv^2-0.5mvi^2.I also know that the work by force of gravity is the same for both objects. I don't understand why the objects would be the same speed at the finish line.
Homework Statement
Kerry is pulling a 156-kg sled along a snowy, horizontal path with a 620-N force directed at an angle of 29.0° above the ground. He pulls the sled over a distance of 26.0 m, and the coefficient of kinetic friction between the sled and the ground is 0.0622.
I need to find the...
The question that puzzled me during lecture! :
A block is pushed so that it moves distance L up a ramp (incline angle q ) at constant speed. If there is friction, the magnitude of the work done on the block by friction…(ramp is up and leftwards)
A. is mgsinqL.
B. is less...
Homework Statement
This is a lab I did for physics. In this experiment, a glider starting from rest on an air track is attached to a string. The string is drawn over a pulley with a mass hanger tied to the other end. Work is done by gravity which results in a gain of kinetic energy of the...
Homework Statement
In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as...
For a conventional wings, at high speed or fast roll, the leading edge of the wings will bend downwards. This will decrease angle of attack and subsequently lift. How does AAW make the wings bend the other way round? Is it due to the materials or the shape of the wings that is designed?
If such...
https://www.sciencedaily.com/releases/2017/10/171027085523.htmCurrent federal efforts to revive the coal industry will likely do more harm than good to fragile Appalachian communities transitioning from coal as a major source of employment, according to a new study.
What do you think...
Homework Statement
The speed of the pendulum bob remains constant
as it travels around the circle
(a) Over one complete circle, how
much work does the tension force F do on the bob? (i) A positive amount; (ii) a negative
amount; (iii) zero.
(b) Over one complete circle, how much work does...
Here is a screenshot of the question I deleted on stack physics after they directed me to this forum.
Eratta:
FYI I have tried with g = -9.80 and 58.9 m when the correct solution (I think) is 5.9 rounded two significant figures. Thanks for any help!
Hello first time posting anything like this to people that have a better grasp on these ideas. Please pardon the lack of proper language structure.
So to my understanding that light travels on photons. The light from a source comes out in waves and particles. As it travels redshift will happen...
Homework Statement
x1= -2, x2= 2
F1= 1, F2= -2
Graph in uploaded image
Homework Equations
w= F* del x* cos(theta)
The Attempt at a Solution
I am trying to find the area under the points of F and x but it has an irregular shape and i don't know what to do? Should i do w= (f1-f2)(del x)?[/B]
Homework Statement
[/B]
F =< 2x, e^y + z cos y,sin y >
(a) Find the work done by the force in moving a particle from P(1, 0, 1) to Q(1, 2, −3) along a straight path.
(b) Find the work done by the force in moving a particle from P(1, 0, 1) to Q(1, 2, −3) along the curved path given by C : r(t)...
Adaptive/active/radar cruise control (Update: It is not adaptive cruise control. It is automatic emergency braking) works only at or below 50 miles (per hour) in some high end cars like range rover, and even below that in other cars.
Does anyone know why?Thanks a lot
Homework Statement
I wanted to calculate the force I need to do a push up. I'm 1.7m tall and weight 72kg. The distance between the top of my head and my shoulders (where the shoulder joint would be) is around 0.3m and my arm length is 0.63m.
Homework Equations + The Attempt at a Solution[/B]...
Homework Statement
The 4-kg ball and the attached light rod rotate in the vertical plane about the fixed axis at O. If the assembly is released from rest at and moves under the action of the 60-N force, which is maintained normal to the rod, determine the velocity v of the ball as approaches ...
In the given question part (a) I don't understand why the work done is negative? The answer says that the displacement is along positive x direction (i understand that) while force acting on the particle is along negative x direction ( why is that? since it appears that as the value of x is...
Homework Statement
A great deal of effort has been expended to find “high temperature superconductors”: materials that are superconductors at temperatures higher than the boiling point of liquid nitrogen (77 K). Most of the older superconductors had to be operated with liquid helium (boiling...
1. The problem statement, all variables, and given/known data
How much work does gravity do on a 1.9-mg raindrop as the drop falls to the ground from a cloud 2500 m above the ground?
Homework Equations
W = FΔx
F = ma
The Attempt at a Solution
I thought this problem would be pretty...
Homework Statement
If you apply a force F with the x component =-6.97 N and the y component = 8.47 N on a car which moves along the x-axis by a displacement of 3.37m. What is the work done on the car by your force in J?
Homework Equations
W=Fxd
The Attempt at a Solution
I think that the...
I understand the whole explanation about why static friction does no work-- I'm just confused about one of the consequences of that.
Consider the picture above. The ring is being pulled down the incline with a force of mg*sin(θ). If you analyze the system about the axis at the center of mass of...
I go to work on the train and I get on at the back and get off at the front. I can choose when to walk through the train. If I walk when the train is accelerating forwards it is harder for me to get to the front and I do more work. If I make the trip when the train is stopped or at a constant...
Hello,
I am confused about the work energy theorem.
If someone goes up the stairs at a constant velocity, is work being done on the person? After all, Wnet = change in kinetic energy, and that change is zero.
This is the original problem that I am trying to solve, from David Morin's Problems...
Homework Statement
I found this algorithm online for computing ln(x). I use the babylonians method for computing square root if it is relevant.
fun naturalLog(desired: Double): Double {
var naturalLog = desired // desired = x
for(number in 0..9) {
naturalLog =...
Why does it cost roughly the same effort to run against an inclined treadmill as up a hill of the same inclination? That is neglecting the movement of the legs and the bobbing up and down as we run and the wind resistance. I remember being told in school physics that there is no work done unless...
Homework Statement
A boy pulls a sled (mass m=59.2 kg) along the ground using a force of magnitude F = 586 N inclined at an angle of θ=37.3° to the horizontal. There is friction between the sled and the ground with a coefficient of µk = 0.205. If the sled starts at rest, how much kinetic energy...