What is work? Give two example, how
work is done? What is the relation between work & energy (Any three points)
Answers
Answer:
The work W done by a constant force of magnitude F on a point that moves a displacement s in a straight line in the direction of the force is the product
{\displaystyle W=Fs} {\displaystyle W=Fs}.
For example, if a force of 10 newtons (F = 10 N) acts along a point that travels 2 metres (s = 2 m), then W = Fs = (10 N) (2 m) = 20 J. This is approximately the work done lifting a 1 kg object from ground level to over a person's head against the force of gravity.
The work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance.
Work is closely related to energy. The work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. Conversely, a decrease in kinetic energy is caused by an equal amount of negative work done by the resultant force.
From Newton's second law, it can be shown that work on a free (no fields), rigid (no internal degrees of freedom) body, is equal to the change in kinetic energy KE of the linear velocity and angular velocity of that body,
{\displaystyle W=\Delta KE.} W=\Delta KE.
The work of forces generated by a potential function is known as potential energy and the forces are said to be conservative. Therefore, work on an object that is merely displaced in a conservative force field, without change in velocity or rotation, is equal to minus the change of potential energy PE of the object,
{\displaystyle W=-\Delta PE.} W=-\Delta PE.
These formulas show that work is the energy associated with the action of a force, so work subsequently possesses the physical dimensions, and units, of energy. The work/energy principles discussed here are identical to Electric work/energy principles.
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