Introduction — What is Work According to Physics?
The word ‘work’ means quite different in daily life compared to the terms of physics.
An activity is approved to be work done in scientific terms when a force exerted on an object must cause a displacement to the same direction as the exerted force.
Work can be defined as the product of the force applied in the direction of the object’s displacement and displacement magnitude.
The formula for work is,
W = (F cos θ) d = F. d
Here, W = Work done by the applied force.
F = Force applied.
d = displacement caused by the applied force.
θ = angle between the force vector and the displacement vector.
Units of Work
The SI unit for work is Joule (J). 1 Joule of work is done when a force of 1 Newton displaces an object by 1 meter in the same direction as the force applied.
What are the factors that affect work?
Work done is affected mainly by two components: Force & Displacement.
Force
Force is the component of push or pulls that, if applied to an object, can change the object’s acceleration and velocity, thus changing the position of the object. If no force is applied to an object, work is not done. Force is a vector quantity.
Displacement
The distance between an object’s final position and initial position after a force is exerted on it is known as displacement. Displacement is a vector quantity. If the applied force causes no displacement of the object, then the work done is zero. For example, pushing against an immobile wall is no work done.
Examples of positive work, negative work, and no work
A boy climbing a tree is negative work as the displacement occurs opposite to the direction of gravitational force.
A ball is thrown upwards, and then the ball’s displacement is in the same direction as the force applied. In this case, positive work is done.
A boy pushing against an immobile wall is no work done as the force exerted by the boy produces no displacement.
Understanding the angle between the force vector & the displacement vector
The work done when a force is applied to an object can have three possibilities: positive work, negative work, and zero work. The displacement direction of the force exerted is the primary criterion to detect the type of work done.
Here are simple examples of negative and zero work done.
Consider the formula of work to understand these examples, that is, W = F s cos θ.
Suppose a boy is climbing up a tree. In this case, he is doing work against the direction of gravitational force at 180°. Work done in this case is considered to be negative.
For example, a coolie lifts a box up his head at 90°. Then work done is zero according to gravitational force. Here, the displacement of the box or displacement angle is perpendicular to the force’s direction.
Recommended Articles:
Work Energy Power
Wind Chime- Origin, Creation, and Purpose
What If The Earth Stopped Spinning?
Wave Power
Physics – Wave Number
Various examples in our daily life activities can be classified as work done and work not done according to physics. Some examples of work done are a cow ploughing a field, a man pushing a grocery cart, and a weightlifter lifting a barbell above her head. In each case, a force has been exerted to make an object move. A man packing punches against a wall can not be considered the work done. Despite the force exerted on the wall, it doesn't make it move. Work does not depend on direction as work is a scalar quantity, not a vector quantity. Scalar quantities only have a magnitude. Work can be referred to as the power to exert force in such a way that it changes the position (displacement) of the object in the direction of the force applied. On the other hand, energy can be defined as the capacity to generate or produce work. The completed work generates energy. Consider the force exerted to be ‘F’, and the angle between the force applied and displacement ‘s’ to be θ. Then the formula for work done is, W = F s cos θ The dimensional formula of work is M1 L2 T-2 Mathematically, consider θ (angle between displacement vector and direction of force vector) to be 180°. We know, W= F s cos θ. Now, F s cos 180° = -Fs = -W. Hence, in this case, the work done is negative. For example, pulling out water from a well, work done by gravity when a person climbs a tree, etc., is considered negative work.Physics - Work FAQs
What is an example of work done and work not done?
Does work depends on the direction?
What is the primary difference between work and energy?
What is the formula for work done by exerting force on the body?
What is an example of negative work?
