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Physics
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23 Nov 2019

How is work defined in physics, and how does this compare with theusual meaning of the word work? Is there such a thing as negativework, and if so what does it mean? Is work a vector or a scalar?What are the units of work?

What is kinetic energy, and how do you calculate it? What ispotential energy? Is there only one kind of potential energy? Whatkind of forces store potential energy?


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Lelia Lubowitz
Lelia LubowitzLv2
6 Sep 2019
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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

Which of the following statement are true mechanical energy? Include all that apply.

1.The total amount of mechanical energy of an object is the sum of its potential energy and the kinetic energy.

2. Heat is a form of mechanical energy.

3. The mechanical energy of an object is always conserved.

4. When non-conservative forces do work, energy is transformed from kinetic to potential (or vice versa), but the total mechanical energy is conserved.

5. A bowling ball is mounted from a ceiling by way of a strong cable. It is a drawback and released, allowed to swing as a pendulum. As it swings from its highest position to its lowest position, the total mechanical energy is mostly conserved.

6. When a friction force does work on an object, the total mechanical energy of that object is changed.

7. The total mechanical energy of an object remains constant if the only forces doing work on the object are conservative forces.

8. If an object gains mechanical energy, then one can be certain that a non-conservative force is doing work.

The Nobel Prize for physics was awarded to Robert Hofstadter forexperimental work involving scattering of 20-GeV electrons fromatomic nuclei.


(a) what is the de Broglie wavelength of a beam of 20-GeVelectrons?


(b) how does this wavelength compare to typical size of an atomicnucleus, which is about 10-15 m? (It is impossible toexamine objects with kind of beam whose wave length is much largerthan object in question: the beam will diffract around the objectrather than reflect from it and will thus not produce a sharpimage.)

(c) Does it much matter whether the "20 GeV" here refers to thetotal or just the relativistic kinetic energy of the electrons?

a metal rod of length L=3.0m is free to rotate about a frictionless hinge at one end. The rod is initially at rest and oriented horizontally and then released so that it swings to the bottom. (a) What are all the forces acting on the rod? Which force or forces do work on the rod as it swings? (b) Is the mechanical energy of the rod conserved? (c) Make a sketch showing the rod in its initial orientation and when it is at the bottom of its swing. (d) What is the initial mechanical energy of the rod? Choose the zero of potential energy so that the final PE is zero. (e) if the speed of the end of the rod when it is at its lowest point is vf, what is the final mechanical energy of the rod? Express your answer in terms of vf. (f) find vf.

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