Nivvedan

Now suppose I try to stop a moving ball. When I stop the ball, the ball loses its kinetic energy and I spend some of my energy. And it appears the energy is lost. Because it is not converted to any other form. Please Explain.

Lets suppose I have a fan attached to a motor in complete vacuum. The electrical energy supplied to the motor is converted into the kinetic energy of the fan. Now I replace the motor with another one which rotates in the opposite direction. I keep the switch on till the blades slow down and stop and switch it off before it begins to rotate in the opposite direction. Lets now compare the initial and the final states. The kinetic energy of the fan is the same before and after the event. But I have spent some electrical energy. Has the enegy been lost? If it is lost, then the law of conservation of energy does not hold. I know I am wrong but I don't know where. Because Physics SHOULD work. Please help me.

Why would I want you to sit for my exams, the tree? You know, I am not that anxious to fail. And for your kind notice. This is not any homework. I found this question in my Mathematics textbook for which even my teacher doesn't know the answer. I just wonder if someone could help me out.

Prove that the numbers 49, 4489, 444889, 44448889,..... obtained by inserting 48 into the middle of the preceding mumbers are squares of integers. Please give a formal mathematical proof involving Arithmetic progression or Geometric progression, not just verification.

How can angular momentum be conceptually thought of? I find it easy to visualize linear momentum as how difficult it is to stop a body possessing that momentum or the extent of damage that body causes on hitting another body. But I find it very difficult to conceptually visualize angular momentum. I can do it mathematically but what exactly is it? Can you please help me there? Please explain in simple terms so that I can understand easily.

I read in a book under the definition of power. I’ll give it in the same words. “Work done does not depend on time. For example, If a person A lifts 10 kg load through 5 ft in 2 minutes and person B lifts the same load through the same height in 1 minute, the work done by both the persons is the same, but the rate at which the work is done is not the same. We say that the second person is stronger and has more power. Thus power is defined as the rate of work done.” Now since the work done is same and Work = F x s , F x s is same for both A and B. Since the height to which the persons lift the load is the same, the displacement is the same. So F1 = F2. But F = ma. Since the mass of the body is same, a1 = a2. If the acceleration is the same, then why does A take more time to lift the same body from the ground than B? Has it got something to do with gravity? Can you please explain this?

Work = Force x Displacement. Right? Let’s consider a frictionless space. Here I apply 100N force to a body and it moves with a constant velocity to another point 10 m from the starting position. Then work done = 100 x 10 = 1000J. If I apply a force of 10N to the same body then too it moves with a constant velocity and reaches the same point, it takes more time but definitely reaches it. Since Work is independent of time, work done now is 10 x 10 = 100J. But how come, to move a same body first 1000J work was done and then now only 100J work is done? Some people claim work is done only when there is a change in energy, But the formula is Force x Displacement. If a body at rest is accelerated by a force some people say that the work done is exqual to the change in kinetic energy of the body. But the formula is F x s. It is independent of the kinetic energy. It only depends on the displacement. A force can cause a body to move with a constant velocity, thereby the body will go on and on and on. So the displacement is infinite. So the work done must also be infinite. I thought about it and concluded that only the power of two forces is different but the work done by the two forces is infinite. It’s altogether confusing to me. Can you please tell me if I have got something wrong and explain this to me?

Except that you will repell that exotic matter, it will do no harm to you.

Can you give me the energy expression for an electron? And also, does the energy of an electron decrease, or does the energy of the Energy shell decrease while moving nearer to the nucleus?