What is Work and energy: Definition and 333 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.

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  1. R

    How do I solve this Work and Energy problem?

    Homework Statement Tarzan (mass of 80kg) has an 18m vine stretched horizontally from his hut to a pivot point P, as shown. He uses it to swing across the gorge to visit Jane's hut, starting from rest to conserve energy. One day Jane spoiled his plans by fastening a strong, thin, smooth...
  2. red1312

    How to calculate the distance travelled in work and energy?

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  3. S

    The Energy and Efficiency of Cross-Country Skiing: A Mathematical Analysis

    A cross-country skier ascends a peak and rises 300 m vertically during the ascent. Her mass including clothing skis, poles, shoes and backpack is 65 kg. (a) Find the minimum mechanical work needed to be done by the skier (neglect friction). (b) Why do we not need to consider the skier’s...
  4. S

    Dynamics question: work and energy (spring problem)

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  5. K

    Work and Energy of carnival dinner

    Homework Statement At a carnival, you can try to ring a bell by striking a target with a 9.00-kg hammer. In response, a 0.4-kg metal piece is sent upward toward the bell, which is 5.00 m above. Suppose that 25.0% of the hammer’s kinetic energy is used to do the (non- conservative) work of...
  6. K

    Work and Energy of wrecking ball

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  7. K

    Work and Energy of snow

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  8. G

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  9. D

    Work and Energy Question

    Homework Statement A person starts to mow a lawn with 50kg old fashioned push lawn mower. The handle of the mower makes an angle of 45 degrees with the sure of the lawn. A 200 N force is applied along the handle of the mower by the person a. Determine the normal force exerted by the ground on...
  10. P

    Calculate speed (work and energy)

    A vertical spring with spring constant 300 N/m is compressed 0.06 m and a 0.25 kg ball placed on top. The spring is released and the ball flies vertically upward. What is the ball's speed when it has gone 0.1 m high? I don't know which relationship is required to find the speed, Can someone...
  11. Naomi

    Work and Energy Problem. Why not include PE?

    Homework Statement Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of rolling friction as the truck tires sink into...
  12. E

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    I thought of this recently, and want to know if there's something I'm missing. So, say a very fragile object decelerates to a stop from a given velocity. For example, a free-falling object hitting the ground. But, all the kinetic energy is absorbed through use of some clever mechanics (assume...
  13. T

    How much work is done on a crate pushed along an incline with constant velocity?

    Homework Statement 40 kg crate is pushed at a constant velocity along an incline with a vertical height of 4 m and inclined distance of 7 m. How much work was done on the crate in moving it to the top of the ramp? For the incline, think of a right angle triangle with the 7 m being the...
  14. F

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    I'm going through a few exercises on Schaum's outline college physics, the section on work and energy. It says "In general, the work done against gravity in lifting an object of mass m through a vertical distance is mgh". So they are basically saying that the work donde to lift an object is...
  15. J

    Trying to understand Work and Energy

    I understand that: 1) For work to be done there must be a force (or a component of it) exerted upon an object, causing it to move. Work done on a system puts energy into it. 2) If the force is applied in the opposite direction to that of the object’s displacement, then the work done by that...
  16. E

    Why does it take more fuel to accelerate a body to a higher speed?

    I apologise for what is probably merely stupidity on my part, but has been vexing me for rather a while, and no one I ask can provide any insight. A body undergoes two accelerations. The first is from 0 to 10 m/s, the second from 10 to 20 m/s. For simplicity's sake I will say F= 1N, a= 1 m/s2...
  17. E

    Principle of work and energy to a collar and spring system, been stuck for hours

    Homework Statement I've been attempting this problem all day now. My current submissions are 10.6N and I keep getting 7.04N every time I retry it but this is also wrong. Can somebody please help me out so I can figure out what I'm doing wrong? Thanks for any help in advanced! The 3.35kg collar...
  18. B

    Who knew finding Velocity could take so much Work and Energy?

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  19. omarMihilmy

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  20. A

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  21. F

    What is Negative Work and Energy?

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  22. J

    Difference between Work and Energy?

    If I say 'a system has 5 Joule energy' then will it be equivalent of saying 'a system can do 5 Joule of work' ? And also will it be equivalent to say 'a system can give 5 watt of power for 1 second' ? If so, then which is the basic property of a system? Work, Power or Energy?
  23. R

    Work and Energy: Springs

    Homework Statement A block of mass m is suspended through a spring of spring constant k[I/] and is in equilibrium. A sharp blow gives the block an initial downward velocity v. How far below the equilibrum position does the block come to an instantaneous rest? Homework Equations...
  24. A

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  25. N

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  26. S

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  27. S

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  28. K

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  29. Y

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  30. B

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  31. A

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  32. M

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  33. Z

    Finding Velocity at B Using Kinetics and Work-Energy Principle

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  34. P

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  35. L

    Work and energy (change in potential)

    Homework Statement part a and b are solved(is it correct), but I am not sure how to solve part c. A single constant force F = (3.02i + 5.45j)N acts on a 3.69kg particle. a) Calculate the work done by this force if the particle moves from the origin to the point having the vector...
  36. P

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  37. B

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  38. M

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  39. P

    Work & Energy: Understanding Negative Work & Potential Energy Gain

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  40. X

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  41. B

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  42. M

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  43. M

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  44. M

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  45. S

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  46. W

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  47. W

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  48. G

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  49. P

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  50. P

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