In this section we\'ll clarify the meaning of work. A student pushes hard enough
ID: 2075258 • Letter: I
Question
In this section we'll clarify the meaning of work. A student pushes hard enough on a wall that she breaks a sweat. The wall, however. Does not move; and you can neglect the tiny amount it compresses? Does the student do any work on the wall? Answer using: your intuition. The physics definition of work. B. Apparently, some reconciliation is needed. We'll lead you through it. In this scenario, does the student give the wall any kinetic or potential energy? Does the student expend energy, i.e., use up chemical energy stored in her body? If the energy "spent" by the student doesn't go into the wall's mechanical energy, where does it go? Is it just gone, or is it transformed into something else? C. Intuitively, when you push on a wall, are you doing useful work or arc you "wasting energy"? D. A student says, 'In everyday life, 'doing work' means the something as 'expending energy.' But in physics, work corresponds more closely to the intuitive idea of useful work, work that accomplishes something, as opposed to just wasting energy. That's why it's possible to expend energy without doing work in the physics sense." In what ways do you agree or disagree with the student's analysis?Explanation / Answer
A)
1) Student do no work.
2) We know Work done= Force x displacement. Since wall doesnot move, the displacement of wall is zero. hence work done is zero.
B)
1. Sice the student is not moving anywhere, his kinetic enrgy is zero. So he is offering potential energy to the wall.
2. Yes student is expanding which is stored in his body in the form of chemical energy.
3. Since wall is not moved , chemical energy of the student will transformed in to heat energy.
C. Its a waste of energy, because work done on the wall produce nothing as it is not moving.
D) Yes it is possible to expand energy without doing work. Think about an electron rotating in circular orbit under magnetic force. In a circular path since starting and ending point are same, the work done by the magnetic force is zeroi. So net work done is zero. But we find there is expansion in energy because there is a radiation which emits because of the rotation of the electrons in circular orbit.
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