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Q. No.A person trying to lose weight by burning fat lifts a mass of \(10~\text{kg}\) upto a height of \(1~\text{m}\) \(1000\) times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies \(3.8\times 10^7~\text{J}\) of energy per kg which is converted to mechanical energy with a \(20\%\) efficiency rate. Take \(g= 9.8~\text{ms}^{-2}\):
1. \(2.45\times 10^{-3}~\text{kg}\)
2. \(6.45\times 10^{-3}~\text{kg}\)
3. \(9.89\times 10^{-3}~\text{kg}\)
4. \(12.89\times 10^{-3}~\text{kg}\)
Subtopic: Gravitational Potential Energy |
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Water is falling from a \(40\) m high dam at the rate of \(9 \times 10^4\) kg per hour. Fifty percent of gravitational potential energy can be converted into electrical energy. Using this hydroelectric energy number of \(100\) W bulbs, that can be lit, is:
(Take \(g=10\) ms–2)
1. \(25\)
2. \(50\)
3. \(100\)
4. \(18\)
(Take \(g=10\) ms–2)
1. \(25\)
2. \(50\)
3. \(100\)
4. \(18\)
Subtopic: Gravitational Potential Energy |
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JEE
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In the given figure, the block of mass \(\mathrm{m}\) is dropped from point \(\mathrm{A}.\) The expression for the kinetic energy of the block when it reaches point \(\mathrm{B}\) is:
1. \(\frac{1}{2} \mathrm{mg}_{0}^{2} \)
2. \(\frac{1}{2} \mathrm{mgy}^{2} \)
3. \(\mathrm{mg}\left(\mathrm y-\mathrm y_{0}\right) \)
4. \(\mathrm{mgy}_{0}\)
1. \(\frac{1}{2} \mathrm{mg}_{0}^{2} \)
2. \(\frac{1}{2} \mathrm{mgy}^{2} \)
3. \(\mathrm{mg}\left(\mathrm y-\mathrm y_{0}\right) \)
4. \(\mathrm{mgy}_{0}\)
Subtopic: Gravitational Potential Energy |
From NCERT
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Two cylindrical vessels having equal cross-sectional areas of \(16\) cm2 contain water up to heights \(100\) cm and \(150\) cm respectively. The vessels are interconnected so that the water levels in them become equal. The work done by the force of gravity during the process is:
[Take density of water = \(10^3\) kg/m3 and \(g\) = \(10\) ms–2 ]
1. \(0.25\) J
2. \(1\) J
3. \(8\) J
4. \(12\) J
[Take density of water = \(10^3\) kg/m3 and \(g\) = \(10\) ms–2 ]
1. \(0.25\) J
2. \(1\) J
3. \(8\) J
4. \(12\) J
Subtopic: Gravitational Potential Energy |
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From NCERT
JEE
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