Work-energy Definition and 168 Threads

  1. D

    Problems On Work-Energy Theorem

    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...
  2. J

    What is the Total Work Equation for Changing an Object's Vertical Position?

    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...
  3. R

    Fallacy in Work-Energy theorem?

    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...
  4. C

    A Difficult Mechanics Problem (Work-Energy?)

    The string is L = 1m long. Peg P is located d below the support point. When the ball is released from rest (as shown), it swings along the dashed path. WHen it catches on the peg, it swings upward but does not complete a circular path. Instead it leaves its path and strikes the peg. Part A...
  5. M

    2 Things: Work-Energy theorem and parabolic trajectories.

    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...
  6. P

    Work-Energy Theorem: Find Final Speed of Ship

    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...
  7. B

    Deriving the work-energy theorem

    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...
  8. N

    Solve Work-Energy Problems: Skier on Hill & Cliff Jump

    Hello. I'm having a lot of trouble with two problems from a homework assignment. I've spent a good amount of time on both problems but just can't seem to get an answer! A step-by-step or suggestions would be most helpful. Thanks in advance! 1. A skier starts from rest at the top of a hill...
  9. P

    Answer:Work-Energy Scaling: R_k,R_w = 3,1

    A particle of mass M moves along a straight line with initial speed v_i. A force of magnitude Fpushes the particle a distance D along the direction of its motion. assume that the particle's mass is increased to 3M. B.)By what multiplicative factor R_k does the initial kinetic energy...
  10. P

    Inclined Plane Friction Question

    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...
  11. P

    Solve Work-Energy Question with Physics Problem | Elastic Cord and Sandbag

    Hi, I am having diffculty with a physics problem. If anyone could help me out it would be greatly appreciated. Question: One end of a long elastic cord is tied to the railing of a high bridge. The other end is tied to a sandbag with a mass of 23.2 kg. The unstretched length of the...
  12. K

    Solve for Length of Friction-Ridden Ice Patch | Work-Energy Theorem Hint

    I've been working on a problem and I'm stumped :| I'm usually pretty good at deriving the equations for problems and solving them once I find out what I need to be solved. But this one is a bit too ambiguous for me, and I'm looking for a few hints :) Anything is appreciated! On an essentially...
  13. S

    How Is Power Calculated in a Simple Work-Energy Problem?

    A force of 5N acts on a 2 kg object that starts from rest. When the force has been acting for 2 s, the rate at which it is doing work is: Here's how I tried to solve it. Solve for acceleration, which I assumed was constant. a = F/m = 5N / 2kg = 2.5 m/s/s Then use the...
  14. B

    Kinetic Energy and Work-Energy Theorem

    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...
  15. O

    Tackling the Work-Energy Theorem

    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...
  16. V

    How Does the Work-Energy Principle Apply in a Car Collision?

    Need help on work-energy principle! How do work relate to energy? If a car which have kinetic energy of 10,000 Joules. A collide with a wall but the wall doesn't move so does the car do the work on the wall? But in the the book they state that energy spend = workdone. only the wall that...
  17. S

    What Is the Work Required to Accelerate a Proton from 0.5c to 0.7c?

    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...
  18. S

    When would I use the work-energy theorem?

    In my text, we learn that the work done on an object is equal to the change in kinetic energy of that object. It seems to me that this statement requires some restrictions. If I take a an object at rest of mass m and lift to a height h and place it at rest on a shelf, the work I've done is...
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