JEE Main Work, Energy and Power Revision Notes - PDF Download
When a constant force F is applied on the box upon the smooth surface, at a certain point of application, it offers a displacement s.
Mathematically, it can express as W = F s cos Θ
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Θ = the angle between F and s (displayed in the above image)
Here, F cos Θ plays an important role in the work done.
Role of Gravity in Work Done
The work done by gravity is said to be negative if an object is moving in an upward direction. The expression for the statement is,
Wg = - m.g.h
Note: Work done is positive when it is falling from certain heights.
Role of Friction in Work Done
A concept is always there in our mind that the force of friction results in a negative work. However, as per the observation, it is concluded that the work done by friction may be zero, positive, negative or zero according to the condition.
Role of a Variable Force in Work Done
If there is a chance of any alteration or variation of magnitude and direction of a force in a three-dimensional space, the expression can be obtained as a function of the position vector F.
Consider that a force is present in 3 – D space. Also, assume that the force’s magnitude as well as direction changes for some reason.