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JAMB Physics 2023 Paper

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Question : 37

Total: 65

How much work is done against the gravitational force on a 3.0 kg object when it is carried from the ground floor to the roof of a building, a vertical climb of 240 m?

7.2 kJ
4.6 kJ
6.8 kJ
8.4 kJ

Solution:

Concept:

Work done against gravity equals the change in gravitational potential energy.

Explanation:

The work done is given by

W = mgh

.

Here,

m = 3.0\ \mathrm{kg}

,

g = 9.8\ \mathrm{m/s^2}

, and

h = 240\ \mathrm{m}

.

Substitute the values:

W = 3.0 \times 9.8 \times 240

.

This gives

W = 7056\ \mathrm{J}

, which is approximately

7.1\ \mathrm{kJ}

.

Using

g = 10\ \mathrm{m/s^2}

gives

W = 3.0 \times 10 \times 240 = 7200\ \mathrm{J} = 7.2\ \mathrm{kJ}

.

Answer:

A.

7.2\ \mathrm{kJ}

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