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Work Energy Power

Imagine a porter carrying a load on his head. Is he doing any work? Yes, one would say! He would be paid for carrying that load from one place to another. But in terms of Physics he is not doing any work! Again, imagine a man pushing a wall? Do you think he is doing any work? Well, his muscles are contracting and expanding. He may even be sweating. But in Physics, we would say he is not doing any work!


If the porter is carrying a very heavy load for a long distance, we would say he has lot of energy. By this, we mean that he has lot of stamina. If a car can run at a very high speed, we say it is very powerful. So, we relate power to speed. However, it means something different in Physics. Let us understand what is meant by work, power and energy in Physics.

Work and Energy

As we know from the law of conservation of energy: energy is always conserved.

Work is the product of Force and the Distance over which it moves.

Imagine you are pushing a heavy box across the room. The further you move the more work you do!

If W is work, F the force acting at an angle θ and s the distance then.

Energy comes in many shapes.

The ones we look at over here are Kinetic Energy (KE) and Potential Energy (PE)

Here I is the Moment of Inertia of the object (a simple manner in which one can understand moment of inertia is to consider it to be similar to mass in Transitional KE)

where h is the height of the object

where k is the spring constant ( it gives how much a spring will stretch for a unit force) and L is the extension or compression of the spring from the equilibrium position.

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