Allen free lecture on Work, Energy and Power class 11

Download Allen free lecture on Work, Energy and Power class 11

WORKWhenever a force acting on a body, displaces it, work is said to be done by the force.
Work done by a constant force is equal to the scalar product of the force F applied and the displacement d of the point of application, W = F . d
Work is a scalar quantity.

• Work is defined for an interval or displacement; there is no term like instantaneous work similar to instantaneous velocity.
• For a particular displacement, work is independent of time.


• When several forces act, work done by a force, for a particular displacement, is independent of other forces.


• Displacement depends on reference frame so work done by a force is reference frame dependent. 
• Work done by a force can be different in different reference frames.
• Work is done by an energy source or agent that applies the force.


• When q = 0°, force does maximum positive work.
• When q = 180°, force does maximum negative work.

ENERGYis defined as the internal capacity to do work.
When we say that a body has energy it means that it can do work.

Different forms of energy Mechanical energy, electrical energy, optical (light) energy, acoustical (sound), molecular, atomic and nuclear energy etc, are various forms of energy.
These forms of energy can change from one form to the other.

• If K.E. of the body decreases then work done is negative and vice-versa.


• In the above discussion, we have assumed that the work done by the force is effective only in changing the kinetic energy of the body. It should however be remembered that the work done on a body may also be stored in the system in the form of potential energy.


• The kinetic energy depends on the frame of reference.

POWER
Average Power Instantaneous Power When we purchase a car or jeep we are interested in the horsepower of its engine. We know that, usually an engine with large horsepower is most effective in accelerating the automobile.

In many cases, it is useful to know not just the total amount of work being done, but also how fast the work is being done. We define power as the rate at which work is being done.

WORK ENERGY AND POWER CHAPTER 6 ALLEN FREE LECTURE

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