Work
In this article we are going to learn about work, relate with calculation, work done to the magnitude of force and distance moved (W = F x d), recall and use ∆W = F x d = ∆E.
Definition of terms:
Work: is done only when distance is covered because of the force applied. In science the word work has a different meaning from its everyday use. No work is done in the scientific sense by someone standing still holding a heavy pile of books: an upward force is exerted, but no motion results. So, if you exert force on an object and the object move, the work is done. However, if you exert force on an object and the object remain stationery, the work is not done. The unit of work is joule (J).
Calculations of work done:
We can calculate the work done with the help of this equation W = F x d
WHERE:
W is the work done.
F is the force applied.
d is the distance covered or moved in direction.
Worked example:
Question: A laboratory desk door is pushed 3 cm with a force of 0.05 kN by a science student. Calculate the wok done by this student.
Solution: First step; we should list our known and unknown variables.
W = ?
F = 0.05 kN
d = 3 cm
Second step; We should write our equation so that we can place the variables. But we have to convert 0.05 kN to N and convert 3 cm to m. 1 kN = 1 000 N so 0.05 kN = 50 N. 1 m = 100 cm so 3 cm = 0.03 m. Now we can write our equation and place variables.
Our formula: W = F x d
W = F x d
W = 50 N x 0.03 m
W = 1.5 J
The work done is 1.5 J.
Relationship between work and energy:
For work to be done energy must be transferred and the more energy is transferred the more work is done. Therefore, the work done is a measure of the amount of energy transferred.
We can relate work and energy with the equation:
Work done = F x d and Energy transferred = F x d.
In other words work done (W) is equal to energy transferred (E) and both measured in joules (J). Therefore, in the example above energy transferred is 1.5 J.