Work done against gravity in lifting a 5 kg box through a distance of 1.5 m is (g=10 ms-2):
Correct answer: D. 75 J
- A. -75 J
- B. -73.5 J
- C. 73.5 J
- D. 75 J
Explanation
The correct answer is 75 J. To find the work done against gravity, you use the formula W = m * g * h. Here, the mass (m) is 5 kg, the gravitational acceleration (g) is 10 m/s-2, and the height (h) is 1.5 m. Therefore, W = 5 kg * 10 m/s-2 * 1.5 m = 75 J. The work done is positive because the force applied to lift the box is in the same direction as the displacement. The incorrect options either have the wrong magnitude or the wrong sign.
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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