Any action involving the utilization of energy is considered work. Encompassing activities like eating, walking, reading, writing, and running are a few examples of work. Work can be classified into three types: positive work, negative work, and zero work. Let’s uncover and elucidate the concepts of work and energy with brief examples of positive work.
Work
Initiation of any kind of work demands mental and physical effort. The scientific definition of work involves the application of force to an object, causing a discernible change in its position. Scientifically, if an object does not move in response to applied force, no work is done.
For instance, if a person is sitting on a horse stands stationary, according to the scientific definition of work is absent here. Similarly, if a person sitting on a horse and the horse moves around, it is recognised as work performed.
Work can be defined as the force applied to an object that causes it to move in any direction. The concept of work incorporates both the applied force and the distance covered by the object. I.e, work measures the energy expenditure involved in moving an object.
The SI unit of work is the unit of energy, which is the Joule (J).
1 J is equivalent to 1 N m, where force is measured in Newtons (N) and distance is measured in meters (m). This relationship arises because the product of force and displacement results in N m, and this is equal to 1 J.
Both force and distance are categorized as vector quantities since they exhibit both magnitude and direction. However, being the product of force and displacement/distance, work lacks direction and only has magnitude. Therefore work is a scalar quantity.
Work Done Against Gravity
Gravity is the fundamental force of attraction that draws objects toward the surface of the Earth.
The measurement of energy expended when force is applied against gravity defines the work done against gravitational pull.
The phenomenon where any object falls on the ground is caused by gravity. Picking that object requires the application of energy i.e. work.
The formula for work (W) is given by multiplying force (F) and displacement (d): W = F * d.
Additionally, the gravitational force (F) is determined by multiplying mass (m) and acceleration due to gravity (g): F = m * g.
When determining the work done against gravity, the displacement of the object is represented by the height it falls to Earth. Hence, the distance (d) is equivalent to the height of the object above the Earth’s surface (h).
Conclusion being:
W = F * d or W = m * g * h, with the SI unit being Joule (J).
Positive Work Done
When the force applied aligns with the motion of the object resulting in work in the direction of movement is called positive work.
Take the scenario of an object plummeting to Earth—its downward trajectory coincides with the force of gravity. Since gravity acts downward in alignment with the falling object, the work done is considered positive work.
W = ( + ) F * d
Negative Work Done
Work done is considered negative when the applied force counteracts the direction of the object’s movement. If the force operates in the opposite direction to the object’s motion, the work done is identified as negative.
Picture an object thrown upward; its motion opposes the gravitational force of the Earth acting downward. Thus, the work done in this scenario is negative.
W = (-) F * d
Zero Work Done
The absence of work occurs when either no force is exerted on the object or when force is applied, but the displacement is zero.
e.g, If force is applied forcefully against a wall without causing any displacement, the work done is zero. In such cases, the measure of energy utilized becomes irrelevant, as it doesn’t result in any object displacement.
Conclusion
In conclusion, work is the consequence of a force that causes the displacement of objects. Positive or negative work is identified by the object’s movement direction concerning the force. When there’s no displacement, the work done is called zero work done. It’s crucial to comprehend work as a scalar quantity, while force and displacement are vectors.
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