Work energy Definition and 186 Threads

for a stream line flow of ideal liquid (non-viscous) imcompressible the sum of pressure energy per unit volume kinetic energy per unit volume , potential energy per unit volume remains constant mathematically P+1/2roV2+ROGH=constant consider a fluid flowing in a pipe of various crossections we...

Homework Statement An object is traveling at 10m/s. along an inclined surface of an angle 10°. How far does it go up the bank? How fast will it be going when it travels back down? Coefficient of friction is .15 Homework Equations Ei = Ef Ef - Ei = Eloss [/B] W = Fd The Attempt at a Solution...

Mentor's Note: This post and another have been merged at the member's request in order to attach their results. 1. Homework Statement See the attached picture for the lab setup. It is all about releasing a cart of 1.212 kg attached with a string and hanging masses. I recorded the Initial and...

The reason why the work energy theorem " ΣW = Δ KE " only includes kinetic and not potential energy, is because gravity undoes the potential energy ? What I mean by "undoes" here is, If you were to, for e.g., lift an apple up a vertical distance, but also accelerate it while lifting it. Then...

if w = - change in epe why does power = +epe / time if power is supposed to equal w / t shouldn't it be equal to -EPE / time Please help me clarify this. epe= electric potential energy and also if current equals to Q/t is there a negative current if there is a negative charge? isn't current...

What is the difference between work done on an object and work done by you? For example, you exert a 100N force pushing a 10kg mass 3.0m across the floor with a coefficient of friction 0.60 1) what is the work done on the mass? 2) what is the work done by you? For question 1 I think it has to...

1. The problem states: Problem 9-72a: The system shown in the figure below consists of a m1 = 4.24-kg block resting on a frictionless horizontal ledge. This block is attached to a string that passes over a pulley, and the other end of the string is attached to a hanging m2 = 2.12-kg block...

Homework Statement The work-energy theorem relates the change in kinetic energy of a particle to the work done on it by an external force: \triangle K = W = \int F\, dx . Writing Newton's second law as F = \frac{dp}{dt} , show that W = \int v\, dp and integrate by parts using the...

Homework Statement A dockworker allows a 350-N crate to slide down an incline that is 8 m in length to the deck of a ship 5 m below the dock level. The rough incline exerts a frictional force of 50 N on the crate. (a) What is the speed of the crate as it reaches the deck (b) What is the...

Homework Statement When Θ=0, the assembly is held at rest, and the torsional spring is untwisted. If the assembly is released and falls downward, determine its angular velocity at the instant Θ=90°. Rod AB has a mass of 6kg, and disk has a mass of 9kg. Rod is 450mm and disk has a radius of...

Homework Statement http://postimg.org/image/m9wtlg5ah/ taking T1 for example why does the disk have no translational kinetic energy component? And why does the friction do no work? Homework Equations Kinetic energy of a rigid body in planar motion T = ##\frac{1}{2}m{v_G}^2...

When does the Kinetic Work Energy Theorem not apply to a situation? Or better, is there a general form of the equation where work can equal the change in any energy? What is work besides a force and a distance?

Homework Statement A small steel ball of mass .0283kg is placed on the end of a plunger of length .0051m attached to a spring 1.88m above the ground. The spring is pre-compressed .0011m and has a spring constant of 177 N/m. The plunger is then angled on a ramp 45° above the horizontal, and is...

Consider a solid sphere and a cube of equal mass, both on a frictionless table. Now, you apply a force to both objects at the point of contact between the object and the table. Then the linear accelerations of both objects will be the same (since the same force is applied to the two objects of...

How do we know that the work-energy theorem holds for variable mass systems? Or rather, since I'm sure that we can at least know it to be true experimentally, what is the mathematical basis for the work-energy theorem? I know for fixed mass systems, a rather simple derivation comes from...

Homework Statement A 1.3kg stone is whirled in a vertical circle at the end of a 0.83m long string. The tension in the string at the top of the circle is 6.4N. What is the tension in the string when the stone is at the bottom of the circle? Homework Equations Fc= mac W=|F||Δd|cosθ...

Hi, After reading several resources about work and energy, I am confused about the conditions that should be satisfied in order to be able to apply work energy theorem. It seems that textbooks have different arguments about this issue. I can summarize what textbooks say in three different...

Homework Statement A 392-N wheel comes off a moving truck and rolls without slipping along a highway. At the bottom of a hill, it is rotating at 25.0rad/s. The radius of the wheel is .6m and its moment of inertia about its rotation axis is 0.800MR2. Friction does work on the wheel as it...

Homework Statement Gasoline has an energy content of about 132.65 MJ/US Gallon. An average passenger car has a mass of 1500kg. The average vehicle experiences a drag force F(drag) = (0.176 kg/m)v^2, regardless of road conditions. A uniform and level road surface provides a 'rolling...

Homework Statement Homework Equations W=F*delta x Fg = mg The Attempt at a Solution I just want to know if my answer is correct for question 4.1.2: W=Fapp*delta x 377860 = Fapp*70 Fapp = 5398N Fnet = 0 (constant velocity) Fnet = 0 5398-8-Fg=0 Fg = 5390 Fg = mg...

Homework Statement I do not know how to find the height. I am thinking of using mgh=delta k but I am not getting the correct answer. I know the answer is 6.28m because my teacher gave it to me. Below is the picture and question: Homework Equations mgh = delta kThe Attempt at a Solution ep=ek...

Homework Statement A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter. An 720-kg helicopter rises from rest to a speed of 7.5 m/s in a time of 5.0 s. During this time it climbs to a height of 7.9 m...

when you push your bicycle up on an incline the potential energy of the bicycle and yourself increases. Where does this energy come from?

Plz tell me Which is correct form of Work Energy theorem 1. Total Work = Toatl change in Mechanical Energy(Potental + Kinetic) 2. Total Work + Potential Energy = Total Change in Kinetic Energy 3. Total Work = Total Change in Kinetic Energy (Mention in the textbooks) Actually i am confused...

I need to solve a work energy equation for height that has initial velocity, final velocity, and work done by friction as the only givens, I don't want to give the full problem, but I can't even find how to do that in my physics book so any help would be appreciated. right now I have...

Homework Statement Using work energy theorem, solve: The Attempt at a Solution The actual answer (3.11s) is exactly half of my answer. Does anyone know what I did wrong?

Homework Statement As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. When you push the platform, you compress the springs. You do 80.0 J of work when...

Homework Statement A pump is required to lift 800 kg of water (about 210 gallons) per minute from a well 14.0 m deep and eject it with a speed of 8ms-1 (a) How much work is done per minute in lifting the water? (b) How much work is done in giving the water the kinetic energy it has when...

Homework Statement At a waterpark, sleds with riders are sent along a slippery, horizontal surface by the release of a large compressed spring. The spring with force constant and negligible mass rests on the frictionless horizontal surface. One end is in contact with a stationary wall. A...

I just wanted to start a thread about the basic concepts of work and energy to clarify some things I have been wondering about. Firstly, work and kinetic energy are concepts independent of force fields; right? Am I right to think that the relationship of force and kinetic energy with respect to...

I came across a rather confusing topic about Work Energy Theorem and Potential Energy applied in lifting a particle.I will be glad if anyone clears it for me. Consider a particle at a height =0.Potential Energy is considered as zero at height=0.Now it is lifted to a position where height is h...

Homework Statement The Attempt at a Solution Is this correct? Is the change in potential energy Ufinal-Uinitial? My answer turns out to be a positive number, so intuitively does this mean that some of the kinetic energy went into potential and thus the final potential energy is greater than...

Homework Statement Homework Equations Inertia about pin = ml^2/3 Work done by rotation = M*theta = 0.5(Inertia about pin) *ω2 The Attempt at a Solution I tried two different methods and both came out to be the same answer. However they did not correspond to any of the multiple...

A small bead of mass m is moving on a smooth circular wire (radius R) under the action of a force F directed towards a point P at a distance R/2 from the centre .What should be the minimum velocity of the bead at the point where it is closest to P so that it may complete the circle. I worked it...

A girl and her sledge have a combined mass of 40kg. She starts from rest and descends a slope which is inclined at 25 degrees to the horizontal. At the bottom of the slope the ground becomes horizontal for 15m before rising at 6 degrees to the horizontal. The girl travels 25m up the slope before...

Homework Statement I don't how how to work out for the Gravitational Energy "H". Info given is 1.5rev converting to 9.42rad/s S=rδ S=0.2x9.42 =1.884 *Should i multiply the axle radius or wheel? The Attempt at a Solution E1=K1+G1+S1 =1/2(8.5)202+(20)(9.81)(H)+0Thanks

Homework Statement Reference to part C of the question, I would like to ask for work done U1to2, how come linear motion is not included? I thought both linear and rotational exist since the parcel "move downwards" (linear) and the wheel is rotating (rotational) Thanks...

Homework Statement Hi guys, I would like to ask for this particular question, The GPE is 0 for all position is because I set datum as the original position, GPE = 0 and when the string got detached from the axle, there is no GPE for datum 2. Am I right? Thanks

Homework Statement From my textbook there is a note that says " A reference datum must always be define in order to obtain the height h. I don't quite understand what is it trying to tell me. I already had define my datum 1 as position 1 and datum 2 as position 2. On my 2nd diagram , I...

Homework Statement A pile driver has a hammer head of mass 4000 kg which is repeatedly raised 3.0 m above a pile and dropped onto it. The force required to drive the pile downwards into the ground is 500 000 N. When the hammerhead is dropped, all the energy foes into moving the pile. How far...

Homework Statement A 5.0 kg box is sliding across the floor at 2.0 m/s when it is accelerated to 8.00 m/s in 1.8 s. If the coefficient of friction is .220 how much power is required to accelerate the box? m = 5.0 kg vi= 2.0 m/s vf = 8.00 m/s change in time = 1.8 s coefficient = .22...

Just a little confused, when work is done on an object it's energy increases right? (i.e. Work done on object = Change P.E + Change K.E + Work done by object) So how come when gravitational force does work on an object(i.e. it falls) the potential energy decreases instead. So its like Work...

Homework Statement Spiderman, whose mass is 80.0 kg, is dangling on the free end of a 12.0 m long rope, the other end of which is fixed to a tree limb above. By repeatedly bending at the waist, he is able to get the rope in motion, eventually getting it to swing enough that he can reach a...

Homework Statement A crate of mass 10.0 kg is pulled up a rough incline with an initial speed of 1.5 m/s. The pulling force is 100 N parallel to the incline which makes an angle of 20.0° with the horizontal. The coefficient of kinetic friction is .4 and the cart is pulled 5.00 m. e) What is...

Homework Statement A net force along the x-axis that has x-component F(x)= -12.0N + (0.300 N/m^2)x^2 is applied to a 3.70 kg object that is initially at the origin and moving in the -x-direction with a speed of 8.80 m/s . Homework Equations w= f * s w= ∫F(x)dx (varying forces)...

Homework Statement There are three boxes stacked on top of each other. Each of the boxes has a mass of 250 kg. There is a chord attached to the bottom box applying a force of 7,000N. The coefficient of static and kinetic friction are: μs = .950 and μk = .900. What is the work net if the boxes...

Homework Statement A baseball is thrown from the roof of 21.7 -tall building with an initial velocity of magnitude 13.2 and directed at an angle of 55.0 above the horizontal. What is the speed of the ball just before it strikes the ground? Use energy methods and ignore air resistance...

Homework Statement A moving electron has kinetic energy K1 . After a net amount of work W has been done on it, the electron is moving one-quarter as fast in the opposite direction. A) Find W in terms of K1 B) Does your answer depend o the final direction of the electrons motion? No...

Please forgive me if the answer to this question is obvious, I studied Political Science for three years in undergrad before I realized 'real' science was far more rewarding. My question (not homework): I understand that Work-Energy can be used for projectile motion, if what you're after is...

If a ball, mass 10kg, is displaced 5m by a gravitational acceleration or 10 m/s², what is the work done by the gravity, and what is the change in kinetic energy of the ball?