Question

Which of the following describes work?

Answer 1

Answer:

• lifting a 1 kg mass 1 m.

Explanation:

Work is the result of applying a force that manages to move a mass.

Thus, the work (mechanical work in this case because this is a mechanical force, not an electrical one) applied by a constant force is the product of the force times the distance that the object is moved.

Also, you can calculate the mechanical work as the difference in the mechanical energy between the initial and the final stages of the event where the force was applied.

Let's see each choice:

a) Holding a mass for 1 hr: since no translation is involved, displacement is and the work is zero.

b) Holding 1 kg mass: again, no motion is involved, so there is no work.

c) Moving 1 m in 1 hr: there is not force involved in this statement, so there is not work.

d) lifting a 1 kg mass 1 m: this, indeed, describes a situation where work results from applying a lifting force to move a mass 1 m up.

In this case, such work is equal to the change in the potential energy of the mass: mgΔh = 1kg × 9.8m/s² × 1 m = 9.8 joules.