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Coolie lifts luggage but does no work. give reason |
| Answer» <html><body><p>When we wish to lift something, our <a href="https://interviewquestions.tuteehub.com/tag/muscles-1106602" style="font-weight:bold;" target="_blank" title="Click to know more about MUSCLES">MUSCLES</a> contract. They do so by active transport of ions in and out of the muscle cell. Now, the crucial point is that the muscle cell is not in equilibrium. Ion concentrations across the membrane are not equal, and hence ions <a href="https://interviewquestions.tuteehub.com/tag/tend-1241588" style="font-weight:bold;" target="_blank" title="Click to know more about TEND">TEND</a> to diffuse, leading to equalisation of concentrations and the relaxation of the muscle cell. To <a href="https://interviewquestions.tuteehub.com/tag/prevent-1164833" style="font-weight:bold;" target="_blank" title="Click to know more about PREVENT">PREVENT</a> this from happening, the cell has to <a href="https://interviewquestions.tuteehub.com/tag/continue-409821" style="font-weight:bold;" target="_blank" title="Click to know more about CONTINUE">CONTINUE</a> to actively transport ions, which is where work is done, against the concentration gradient!When we wish to lift something, our muscles contract. They do so by active transport of ions in and out of the muscle cell. Now, the crucial point is that the muscle cell is not in equilibrium. Ion concentrations across the membrane are not equal, and hence ions tend to diffuse, leading to equalisation of concentrations and the relaxation of the muscle cell. To prevent this from happening, the cell has to continue to actively transport ions, which is where work is done, against the concentration gradient!This does not happen, e.g. with a table. The molecules of the table are in an equilibrium configuration. When you place a weight on the table, the molecules shift into a new equilibrium configuration. No work is needed to keep it in the new configuration, so no change in <a href="https://interviewquestions.tuteehub.com/tag/energy-15288" style="font-weight:bold;" target="_blank" title="Click to know more about ENERGY">ENERGY</a> takes place. A muscle cell, in its relaxed state, is in an equilibrium state; in a contracted state, it is not in equilibrium and needs work to be done to maintain it in such a state...</p></body></html> | |