Lifting to the 20th floor requires twice the energy because the vertical height is doubled. However, since the time taken is also doubled, the power required remains exactly the same as before.
A crane lifts a mass m to the 10th floor of a building in a certain time. It then raises the same mass to the 20th floor of the same building in double the time. How much more energy and power are required? Assume that the height of all floors is equal.
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Reaching the 20th floor doubles the vertical displacement compared to the 10th floor, so the required energy m g h doubles, requiring one hundred percent more energy. Power is work divided by time. Because both work and time double simultaneously, the ratio of work to time remains constant. Therefore, no additional power is required and the power required remains the same.
For more NCERT Solutions of Class 9 Science Exploration Chapter 7 Work, Energy and Simple Machines Question Answer (2026-27)
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