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JAMB Physics 2013 Paper

Question : 9

Total: 43

Solution:

Concept:

Power is the rate at which work is done against gravity.

Explanation:

Work done by the pump equals the gravitational potential energy gained by the water:

W = mgh

Substitute the given values:

m = 5000\ \mathrm{kg}

g = 10\ \mathrm{m\,s^{-2}}

h = 60\ \mathrm{m}

So,

W = 5000 \times 10 \times 60 = 3{,}000{,}000\ \mathrm{J}

Time taken is

t = 15\ \mathrm{min} = 15 \times 60 = 900\ \mathrm{s}

Power is

P = \frac{W}{t} = \frac{3{,}000{,}000}{900} = 3333.33\ \mathrm{W}

This is approximately

3.3 \times 10^3\ \mathrm{J\,s^{-1}}

Answer:

3.3 \times 10^3\ \mathrm{J\,s^{-1}}

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