Test Index

WAEC Physics 2013 Paper

Question : 9

Total: 46

Solution:

Concept:

At maximum height, the entire initial kinetic energy is converted into potential energy.

Explanation:

Total time of flight is

1.2\,\mathrm{s}

Time to reach maximum height is

t = \frac{1.2}{2} = 0.6\,\mathrm{s}

Mass of the body is

m = 20\,\mathrm{g} = 0.02\,\mathrm{kg}

Using

v = u - gt

at maximum height, where

v = 0

0 = u - 10(0.6)

u = 6\,\mathrm{m/s}

Maximum height is

h = \frac{u^2}{2g} = \frac{6^2}{2 \times 10} = \frac{36}{20} = 1.8\,\mathrm{m}

Potential energy at maximum height is

P.E. = mgh = 0.02 \times 10 \times 1.8 = 0.36\,\mathrm{J}

Answer:

The potential energy at the maximum height is

0.36\,\mathrm{J}

Correct option: A.

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