Work-energy theorem Definition and 95 Threads

Homework Statement A blue whale materializes 11.5 km above an airless planet with an acceleration of gravity of 6.85 m/s2. What is the speed of the whale right before impact? Use the work energy theorem. Homework Equations Work energy theorem : W = the change in k W=kf - ko w=1/2(mvf2)...

Homework Statement A skier slides down a hill, starting from rest at a height of 250m above the bottom of the hill. She skis over an intermediate hill, whose height is 100m above the bottom of the hill. If resistive forces are neglected, what is the speed of the skier a) at the top of the...

Homework Statement While running at a speed of 5.0m/s Tarzan grabs a 9.0m long vine hanging vertically from a tall tree in the jungle and swings on it. As he swings on the vine, how much work is done on him by the tension force in the vine? To what maximum vertical height can he swing if he...

Homework Statement 490 J of work is done on a pin when a 5 kg sledgehammer strikes it (bringing the sledgehammer to rest). What is the initial speed of the sledge hammer. Homework Equations (Fnet)(d)= (0.5)(m)(velocity final^2 - velocity initial^2) The Attempt at a Solution...

Homework Statement A mass m whirls on a frictionless table, held to circular motion by a string which passes though a hole in the table. The string is slowly pulled through the hole so that the radius of the circle changes from l1 to l2. Show that the work done in pulling the string equals...

Homework Statement A skier comes crashing into the netting at the bottom of a ski hill. The skier has a mass of 85 kg and is moving at a speed of 65 km/h (234 m/s). (a) How much work is done by the netting while bringing the skier to rest? (b) If the "spring" constant for the netting is...

Homework Statement The masses of the javelin, discus, and shot are 0.8kg, 2kg, 7.2kg, respectively, and record throws in the track events using these objects are about 89 m, 69 m, 21 m. respectively. Neglecting air resistance, (a) calculate the minimum kinetic energies that would produce such...

On an essentially frictionless, horizontal ice rink, a skater moving at 6.0 m/s encounters a rough patch that reduces her speed by 42 \% due to a friction force that is 20 \% of her weight. Use the work-energy theorem to find the length of this rough patch. i do: [.42 * (.5) * (6)^2]/ [.2...

Homework Statement It takes 241 kJ of work to accelerate a car from 22.0 m/s to 28.8 m/s. What is the car's mass? W = 241000 J vo = 22.0 m/s vf = 28.8 m/s m = ? Homework Equations KE = 1/2 mv2 W = KEf - KEo The Attempt at a Solution W = KEf - KEo W = 1/2 mvf2 -...

1. You are a member of an alpine rescue team and must project a box of supplies, with mass m, up an incline of constant slope angle alpha so that it reaches a stranded skier who is a vertical distance h above the bottom of the incline. The incline is slippery, but there is some friction present...

Homework Statement Use the Work-Energy Theorem to show that an object with initial velocity vo will travel a distance d across a rough horizontal surface before stopping, where d = vo2/(2muKg). Homework Equations W = delta KE = mV^2/2 The Attempt at a Solution To be honest, I have...

Homework Statement If the speed of a car is increased by 50%, by what factor will the minimum braking distance be increased assuming all else is the same? Ignore the driver's reaction time. Homework Equations W = Fd \cdot cos\theta W = \Delta{E_k} The Attempt at a Solution...

Homework Statement How much work is needed for a 71 kg runner to accelerate from rest to 10.2 m/s? I have no idea how to do this so I have no equations or attmpts at this.

Homework Statement An 1,100 kg car is traveling 46 km/h on a level road. The brakes are applied long enough to remove 51 kJ of energy. A. What is the final speed of the car? B. How much more kinetic energy must be removed by the brakes to stop the car? C. Is this energy really being...

I am just confuse in this question may be i forgot about work and energy .I just need little help not the answer ,here is the question 1.A block of mass 2.2 kg, which has an initial velocity of 3.9 m/s at time t = 0, slides on a horizontal surface. Calculate the work that must be done on...

Homework Statement A 16 g bullet is accelerated in a rifle barrel 72.3 cm long to a speed of 1010 m/s. Use the work-energy theorem to find the average force exerted on the bullet while it is being accelerated. Answer in units of N.Homework Equations W=changeKEThe Attempt at a Solution...

Homework Statement Use the work-energy theorem to solve. A branch falls from the top of a 95 m tall tree, starting from rest. How fast is it moving when it reaches the ground? Neglect air resistance. Homework Equations work-energy theorem:w_total=K_2-K_1 In this problem, K_1 is 0 since it is...

OK, I'm working on a question regarding IRFs, but I seem to be a little confused. Question: Observer A is on the ground and Observer B in on a train moving with uniform velocity v wrt the ground. Each observes that a particle of mass m, initially at rest wrt the train, is acted upon by a...

Two masses are connecte by a ligh string over a light, frictionless pulley the table surface that m2 is on is also frictionless. Apply the work-energy theorem for this system to calculate the speed of the masses after the masses have moved a distance delta x starting from rest. Note that the...

It's been a while since I've taken calculus. I was going through the derivation of the work-energy theorem and came across this: dv/dt = (dv/dx)(dx/dt) which is supposed to be a result of the chain rule. Anyone care to explain and please simplify it as much as possible. Thanks!

Okay, I just took a test where there was a loop with a bar and a resistor in a magnetic field going into the screen as follows ____/\/\/\_____ lxxxxxxxxxxxxxxxlxxx lxxxxxxxxxxxxxxxlxxx lxxxxxxxxxxxxxxxlxxx lxxxxxxxxxxxxxxxlxxx l____(bar)_____lxxx lxxxxxxxxxxxxxxxlxxx lxxxxxxxxxxxxxxxlxxx...

quick question: I have to write about the work-energy theorem, and I've already defined it, but i need to mention a couple of cases where this theorem is applied in daily life around us.. I dont' quite understand where we would use this theorem in everyday life.. just a few simple ideas to...

A particle moving in the x direction is being acted on by a net force F(x)= Cx^2, for some constant C. The particle moves from x_initial= L to x_final= 3L. What is deltaK, the change in kinetic energy of the particle during that time? Express your answer in terms of C and L. I got 16CL^3...

Homework Statement You are a member of an alpine rescue team and must get a box of supplies, with mass 2.60 kg, up an incline of constant slope angle 30.0\circ so that it reaches a stranded skier who is a vertical distance 3.10 m above the bottom of the incline. There is some friction present...

[SOLVED] Work-Energy Theorem I'm sorry that I do seem to require quite a bit of help, but sometimes when the formulas just aren't working for me I get desperate. Homework Statement A force is applied to a 2.5kg- radio-controlled model car parallel to the x-axis as it moves along a...

[SOLVED] Another work-energy theorem problem... Homework Statement An automobile traveling at 45 km/h is brought to a stop in 60 m. Assuming that the same conditions (same braking force, neglect reaction time) hold for all cases, (a) what would be the stopping distance for an initial speed...

[SOLVED] Homework Problem about the Work-Energy Theorem Please help! This is my first year of taking physics and I am really confused... A puck on a shuffleboard decreases in speed from 1.0 m/s to .20 m/s while traveling 4.0 m. What is the coeffecient of kinetic friction between the puck and...

Is this expression always true?: W=\Delta E Please explain why this is using mathematical computations. I understand it conceptually but I just can't connect the two mathematically. Also, why does my book only have the expression: W= \Delta KE rather than: W= \Delta KE + \Delta PE why did...

Two blocks with different mass are attached to either end of a light rope that passes over a light, frictionless pulley that is suspended from the ceiling. The masses are released from rest, and the more massive one starts to descend. After this block has descended a distance 1.00m , its speed...

A ball is launched with initial speed v from ground level up a frictionless slope. The slope makes an angle theta with the horizontal. Using conservation of energy, find the maximum vertical height hmax to which the ball will climb. Express your answer in terms of v, g, and theta. You may or...

Homework Statement A driver in a car is on a level road traveling at a speed of "v". He puts on the brakes and they lock and skid rather than roll. I have to use the Work-Energy Theorem to give an equation for the stopping distance of the car in terms of "v". the acceleration of gravity "g"...

I am compleatly lost on these two KE Work-Energy Theorem Problem questions any feedback or help would be greatly appreciated. Thank you in advance... 1.) 47.0 g golf ball is driven from the tee with an initial speed of 52.0 m/s and rises to a height of 25.0 m. (a) Neglect air resistance...

Take Two: problem using Work-Energy Theorem The only force acting on a 1.5 kg body as it moves along the positive x-axis has an x component Fx = - 6x N, where x is in meters. The velocity of the body at x = 3.0 m is 8.0 m/s. (a) What is the velocity of the body at x = 4.0 m? (b) At what...

This is the problem: You throw a 20-N rock vertically into the air from ground level. You observe that when it is 15.0 m above the ground, it is traveling at 25.0 m/s upward. Use the work-energy theorem to find a) its speed just as it left the ground; b) its maximum height. I drew a...

Please check to see if my calculations are correct. I am unsure if I used the right values and setup. You throw a rock of weight 21.0 N vertically into the air from ground level. You observe that when it is a height 14.8 m above the ground, it is traveling at a speed of 25.7 m/s upward...

i have a Qns. given that i have a 2kg mass on Earth and i want to accelerate from 0 m/s to 10 m/s the work done should be : Workdone = 1/2(m)(V)^2 - 1/2(m)(v)^2 = 1/2(2)(10)^2 -0 = 100 J however, if i were to take my frame of reference from let say space i...

Hello, If the work changes the object's velocity through a horizontal distance then: W = delta KE But, what if the work changes the object's vertical position. Then the object's mph changes. Would the Work formula be: W = delta PE? But, if something is moving upwards (y axis) then...

Fallacy in Work-Energy theorem?? Consider a block moving on a floor which has some friction. It is given an initial velocity of 10 m/s and it comes to rest after some time due to friction. Since friction slows the block down, heat is generated, some of which goes into raising the temperature of...

Hi, When reading through the work-energy thread, i just got reminded of something bugging me for quite a while. I don't think this is mentioned in the work-energy thread, firstly, how can we show that, \int f \bullet ds = \Delta E also, I've heard that there's a way to show that...

I'm having trouble with where to begin with this question, if anyone has guidance I'd be grateful. A spaceship of mass 5.00 x 10^4 kg is traveling at a speed 1.15 x 10^4m/s in outer space. Except for the force generated by its own engine, no other force acts on the ship. As the engine...

In this problem, you will use your prior knowledge to derive one of the most important relationships in mechanics: the work-energy theorem. We will start with a special case: a particle of mass m moving in the x direction at constant acceleration a. During a certain interval of time, the...

Hi. I was wondering if anyone could help me out in this question: A mass M is sliding down the inclined plane at a speed of 2.13 m/s. The mass stops a distance of 2.45 m away from the base of the inclinde, along a flat surface. The mass slides 1.24 m down the incline before reaching the...

Hello, I could use a little guidance on this problem. An extreme skier, starting from rest, coasts down a mountain that makes an angle of 25 degrees with the horizontal. The coefficient of kinetic friction between her skis and the snow is 0.200. She coasts for a distance of 13.1m before...

I'm trying to tackle the work-energy theorum. It has occurred to me that the distance in work: Force x distance is determined by the acceleration in the force variable, and time of force as well. The distance, creates a halving of the final product of the Joule unit, because the...

Can some one help me out here, I have tried using several different methods but I still don't know what I am doing wrong. The question is: A proton in a high energy accelerator moves w/a speed of 0.5c, use the work-energy theorem to find the work required to increase its speed to 0.7c...