Work & Work Done
Work is defined as the force applied over a given distance, and the equation for work is:
Work (W) equals the force (f) times the distance (d) W = f ⋅ d
Work done on an object is equal to the force applied times the distance travelled by the object, whereby both the force and distance are in the same direction. In physics, for something to be quantified as work, the object has to move; holding a bowling ball in one hand for 1 hour doesn’t qualify as work. However, a bowler using applied force to throw the bowling ball down a bowling alley lane would constitute as Work done.
Both force and distance are vector quantities as they have magnitude and direction, but Work is a scalar quantity. The work done due to displacement caused by a force is a scalar quantity, not a vector. Work is considered a scalar quantity because it only has magnitude and no direction. This is because Work is defined as the product of the force applied to an object and the displacement of that object in the direction of the force.
The illustration to the right shows a lady applying force against the wall but pushing against it. Pushing against a wall doesn't count as work in physics because of the definition of work. Work is defined as the product of force and displacement in the direction of that force. Put another way, work is only done when a force causes an object to move a certain distance.
When you push against a wall, you exert a force, but the wall doesn't move. Since there is no displacement, the work done is zero. This is why, in physics, while you may be expending energy in terms of effort or fatigue, it does not qualify as work in the classical mechanical sense. Therefore, force might have been applied to the wall, but the displacement was in a zero direction. Consequently, it does not qualify as work done.
The father pulling his daughter in a trolley below is an example of work done in physics. The father applied 50N (newtons) of force, pulling the object (the trolley with his daughter inside) at a 30-degree angle for 30m (meters). Therefore, the total work done is 50N * 30m = 1500 Joules.
Work is done in weightlifting by increasing the weight on the barbell, dumbbell, or machine or by increasing the distance over which the weightlifter pushes the barbell or weights. When lifting a load, work is done against the force of gravity. The amount of work done equals the force applied multiplied by the distance lifted. This can be expressed mathematically as W = F ⋅ d, where W is the work done, F is the force applied, and d is the distance lifted.
Let's take an example: a weightlifter clean presses a 65-kilogram (kg) barbell (25kg plates on each side and 15kg barbell weight) from the ground by 2 meters (m). The work done on the barbell is against the earth's gravity, which is 9.8 meters per second squared m/s2. Therefore, the work done upon the weight against gravity can be calculated as follows:
Work= 65 x 9.7 = 490 Newtons
Work Done = 490n x 2m = 980 J (Joules)
Work Done = (Mass × acceleration due to gravity) × Displacement
We use joule, a unit of work or energy in the International System of Units (SI), equal to the work done by a force of one newton acting through one meter expressed as Newton • meter (N • m).
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